Ferroic Glasses Research Articles

Hybrid magnon-phonon localization enhances function near ferroic glassy states.

Ferroic materials on the verge of forming ferroic glasses exhibit heightened functionality that is often attributed to competing long- and short-range correlations. However, the physics underlying these enhancements is not well understood. The Ni45Co5Mn36.6In13.4 Heusler alloy is on the edge of forming both spin and strain glasses and exhibits magnetic field-induced shape memory and large magnetocaloric effects, making it a candidate for multicaloric cooling applications. We show using neutron scattering that localized magnon-phonon hybrid modes, which are inherently spread across reciprocal space, act as a bridge between phonons and magnons and result in substantial magnetic field-induced shifts in the phonons, triple the caloric response, and alter phase stability. We attribute these modes to the localization of phonons and magnons by antiphase boundaries coupled to magnetic domains. Because the interplay between short- and long-range correlations is common near ferroic glassy states, our work provides general insights on how glassiness enhances function.

Low-Field-Driven Superior Energy Storage Effect with Excellent Thermal Stability by Constructing Coexistent Glasses.

In this work, we found that the defreezing coexistent glassy ferroelectric states hold significant potential for achieving superior energy storage performance, especially under low fields, by using phase field simulations and experimental approaches. A remarkable room-temperature energy recoverable storage density Wr exceeding 2.7 J/cm3 with a high efficiency η surpassing 80% under a low electric field of 170 kV/cm was obtained in the x = 6-12% compositions of x[Bi(Mg2/3Nb1/3)O3]-(1-x)[0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3-1%MnO2] (BNBT-BMN) ceramics due to the combination of low Pr and high Pm of the coexistent ferroelectric glasses. Intriguingly, the superior Wr and η of the coexistent state of glasses can also be maintained in a wide temperature range of 293-430 K, indicating the excellent thermal stability of the energy storage behavior. Importantly, the Wr and η of this glass coexistent composition increase upon heating from room temperature to 360 K due to the defreezing process, leading to maximum Wr ∼ 2.9 J/cm3 with high efficiency η ∼ 90% of x = 10% at 360 K. When considering both energy storage behavior and thermal stability under low fields (<250 kV/cm), the BNBT-BMN ceramics outperform nearly all lead-free counterparts available today. Consequently, our work not only expands the research scope of ferroic glasses but also establishes a new paradigm for developing superior lead-free dielectrics suitable for high-temperature energy storage devices.

High-Temperature Ferroic Glassy States in SrTiO_{3}-Based Thin Films.

Disordered ferroics hold great promise for next-generation magnetoelectric devices because their lack of symmetry constraints implies negligible hysteresis with low energy costs. However, the transition temperature and the magnitude of polarization and magnetization are still too low to meet application requirements. Here, taking the prototype perovskite of SrTiO_{3} as an instance, we realize a coexisting spin and dipole reentrant glass states in SrTiO_{3} homoepitaxial films via manipulation of local symmetry. Room-temperature saturation magnetization and spontaneous polarization reach ∼ 10 emu/cm^{3} and ∼ 25 μC/cm^{2}, respectively, with high transition temperatures (101K and 236K for spin and dipole glass temperatures and 556K and 1100K for Curie temperatures, respectively). Our atomic-scale investigation points out an underlying mechanism, where the Ti/O-defective unit cells break the local translational and orbital symmetry to drive the formation of unusual slush states. This study advances our understanding of the nature of the intricate couplings of ferroic glasses. Our approach could be applied to numerous perovskite oxides for the simultaneous control of the local magnetic and polar orderings and for the exploration of the underlying physics.

Origin of reentrant relaxor formation in ferroelectric solid solutions

Nanoscale compositional heterogeneity created by doping in ferroelectric systems leads to the formation of conventional relaxors in most cases, but reentrant relaxors in some unusual cases. It has remained a long-standing puzzle why reentrant relaxors rather than conventional relaxors form in these unusual cases. In this study, we use a binary ferroelectric system having a solid solution of a ferroelectric with cubic (C) to tetragonal (T) transition at one end and a ferroelectric with C to rhombohedral (R) transition at the other end, with nanoscale compositional heterogeneities, to reveal the origin of the reentrant relaxor transition. Our phase field simulations based on Landau theory demonstrate that the reentrant relaxor transitions in such a system are manifested by the formation of R nanodomains in the T microdomains upon cooling at compositions near the T/R phase boundary, which is accompanied by frequency-dependent permittivity peaks below ${T}_{\mathrm{C}}$. We found that the difference in phase transition sequence at different local compositions near the T/R phase boundary created by point defect doping is essential for the formation of reentrant relaxors. This work unravels the general conditions for the formation of reentrant relaxors and may shed light on the origin of other reentrant ferroic glasses.

Strain glass in Ti50-x-yNi50+yNby alloys exhibiting a boson peak glassy anomaly

Strain glass, which is a type of ferroic glass with lattice strain short-range ordering, has been found in many shape memory alloy systems, while its unique properties still await to be investigated. Here we report a strain glass found in Ti50-x-yNi50+yNbx due to the synergistic effect of Ni and Nb atoms and its boson peak glassy anomaly. It is found that Nb atoms can only slightly suppress the martensitic transformation, but with the help of 1 at% excess Ni atoms (y=1), 2% Nb atoms (x=2) are enough to lead the system to the strain glass state. A three-dimensional phase diagram is established accordingly. Moreover, a boson-peak-like glassy feature is also found in the strain glass state, which resembles the boson peak in metallic glass. This work provides more clues to understand the glass nature of strain glass.

Ferroic glass behavior in (Bi,Na)TiO3-based lead-free electroceramics

Ferroic glass materials, that is, relaxors, spin glasses, and strain glasses attract special attention because of their intriguing physical properties and potential for novel technological applications. Here, several characterization techniques are used to demonstrate the occurrence of simultaneous relaxor and strain glass states in the ternary lead-free xBi0.5Na0.5TiO3-yBi0.5K0.5TiO3-zBaTiO3 (BNBK) system. Hysteresis and current density loops measurements at different temperatures for a BNBK ceramic showed typical characteristics observed in BNT based ceramics containing the tetragonal P4bm phase. Above 400 K, slim loops like those of ferroelectric relaxors are observed. A phase transition with simultaneous relaxor and strain glass character is revealed by the dielectric and anelastic characterizations, which opens up a wide spectrum of possible applications. The minimum of elastic modulus shifts to higher temperatures as the frequency increases, obeying the Vogel-Fulcher relation, which clearly shows the occurrence of a strain glass state in this material. Similar characteristics are observed in the imaginary part of the dielectric permittivity, which demonstrates the relaxor character of this phase transition. The origin of this phenomenon was elucidated with the help of structural characterizations, such as Raman spectroscopy and high-resolution synchrotron X-ray diffraction, at different temperatures. This work provides an in-depth understanding of the structural changes that determine the phenomenology behind the observed ferroic glass behavior and the ferroelectric, dielectric, and mechanical properties of this ternary ceramic composition.

Magnetic glassy martensite induced reversible magnetocaloric effect in Heusler alloys

Heusler alloys hold great potential to act as cooling medium for next-generation solid state refrigeration due to their substantial entropy changes at field-driven magnetostructural transitions. One of the key impediments in the use of Heusler alloys for efficient cooling lies in the poor reversibility of magnetocaloric effect (MCE). In this work, a highly reversible MCE with large isothermal heat Q of ∼ 4.83–5.3 kJ/kg near room temperature, is achieved in Ni50Mn34In12Ga4 Heusler alloys at the transition between unfrozen canonical spin-glassy martensite and ferromagnetic austenite, crosschecked by indirect and direct methods. Phase field simulations reveal that the presence of spin glass in martensite state can result in reversible field-induced magnetostructural transitions in Heusler alloys, thus effectively circumventing the irreversibility of large MCE at strong first-order transitions without the need of any external stimuli such as mechanical load. The occurrence of such field-induced first-order transitions arose from the negative coupling between magnetic moment and the volume of the material. This work suggests the great power of ferroic glasses in improving the reversibility of promising MCE at first-order phase transitions and may push forward more Heusler alloys close to the practical refrigerant in highly efficient solid-state cooling protocols.

Relaxor ferroelectrics and related superglasses

Mesoscopic ferroic glasses such as martensitic strain glass Ti50−x Ni50+x, magnetic cluster glass La0.7Ca0.3Mn0.7Cd0.3O3, and superdipolar relaxor PbMg1/3Nb2/3O3 (PMN) undergo glass transitions preceded by mesoscopic precursor patterns – elastic or magnetic tweed or polar nanoregions (PNR), respectively. In PMN the PNR glass transition at Tg ≈ 240 K reveals glassy dynamic criticality and non-ergodicity of the field-induced low-T phase similar to that of a superspin glass of fixed magnetic nanoparticles in a diamagnetic environment. A final ferroelectric domain state is reached at Tp ≈ 213 K via PNR percolation, which is absent in weak relaxors like BaTi0.65 Zr0.35O3 (BTZ35).

Materials physics and spin glasses**This paper is dedicated to Giorgio Parisi in celebration of his 70th birthday, in appreciation of his enormously innovative and influential contributions to science and its leadership and in gratitude for his friendship.

Comparisons and analogies are drawn between materials ferroic glasses and conventional spin glasses, in terms of both experiment and theoretical modelling, with inter-system conceptual transfers leading to suggestions of further issues to investigate.

Accelerating ferroic ageing dynamics upon cooling

Once a structural glass is formed, its relaxation time will increase exponentially with decreasing temperature. Thus, the glass has little chance of transforming into a crystal upon further cooling to zero Kelvin. However, a spontaneous transition upon cooling from amorphous to long-range ordered ferroic states has been observed experimentally in ferroelastic, ferroelectric and ferromagnetic materials. The origin for this obvious discrepancy is discussed here conceptually. We present a combined theoretical and numerical study of this phenomenon and show that the diffusive and displacive atomic processes that take place in structural glass and amorphous ferroics, respectively, lead to markedly different temperature-dependent relaxation behaviors, one being ‘colder is slower’ and the other being ‘colder is faster’. Once a structural glass (e.g., window glass) is formed, it will not turn into a crystal upon further cooling to zero Kelvin. This is, however, not true for ferroic glasses — disordered states of magnetization, polarization or strain. Junyan Zhang from Xi'an Jiao Tong University in China and collaborators developed a theoretical framework to shed light on how the relaxation processes in these two types of glasses are fundamentally different, one being dominated by atomic diffusion and activation enthalpy, and the other being dominated by collective displacements and activation volume/entropy; one being ‘colder is slower’ as expected, and the other being ‘colder is faster’. Numerical simulations unveil the change from ‘colder is faster’ to ‘colder is slower’ with an increasing defect concentration in a generic ferroelastic system. Microstructure evolutions upon cooling in three ferroelastic systems having different defect concentrations, c=0.02, 0.14 and 0.40, respectively. Green color in the figures represents the parent phase; blue and red colors represent the two different martensitic variants. As the defect concentration increases, the behavior of the ferroelastic system shifts from ‘the cooler the faster’ (c=0.02 and 0.14) to ‘the cooler the slower’ (c=0.40).

Glass transition in ferroic glass Kx(ND4)1−xD2PO4: a complete x-ray diffraction line shape analysis

Quenching of dynamic disorder in glassy systems is termed as the glass transition. Ferroic glasses belong to the class of paracrystalline materials having crystallographic order in-between that of a perfect crystal and amorphous material, a classic example of ferroic glass is the solid solution of ferroelectric deuterated potassium dihydrogen phosphate and antiferroelectric deuterated ammonium dihydrogen phosphate. Lowering temperature of this ferroic glass can lead to a glass transition to a quenched disordered state. The subtle atomic rearrangement that takes place at such a glass transition can be revealed by careful examination of the temperature induced changes occurring in the x-ray powder diffraction (XRD) patterns of these materials. Hence we report here results of a complete diffraction line shape analysis of the XRD patterns recorded at different temperatures from deuterated mixed crystals DKxA1−xDP with mixing concentration x ranging as 0 < x < 1. Changes observed in diffraction peak shapes have been explained on the basis of structural rearrangements induced by changing O–D–O hydrogen bond dynamics in these paracrystals.

Glass-ferroic composite caused by the crystallization of ferroic glass

We report a glass-ferroic composite (in short ``glass-ferroic'') in ferroic materials, an analog of the composite of glassy and crystalline phases (glass-crystal composite, e.g., semicrystalline polymer). The formation of glass-ferroic (i.e., the existence of residual ferroic glass) stems from a time-dependent crystallization of the ferroic glass. Moreover, glass-ferroics show two types of transition characteristics depending on the thermal hysteresis of crystallization transition as exemplified in $\mathrm{T}{\mathrm{i}}_{48.7}\mathrm{N}{\mathrm{i}}_{51.3}$ and $\mathrm{P}{\mathrm{b}}_{0.87}\mathrm{L}{\mathrm{a}}_{0.13}\mathrm{Z}{\mathrm{r}}_{0.4}\mathrm{T}{\mathrm{i}}_{0.6}{\mathrm{O}}_{3}$. Based on experimental results, a generic phase diagram is established to include all ferroic states, i.e., ferroic crystal, ferroic glass, and glass-ferroic. Being the third class of ferroic materials, glass-ferroics may open a new avenue for achieving novel properties and designing ferroic phase-change memory devices.

Multiple ferroic glasses via ordering

Structural glasses are characterized by the loss of long-range translational and rotational symmetry. In the last two decades, however, it has been discovered that materials that exhibit ferroic (ferromagnetic, ferroelectric and ferroelastic) phase transformations may also exhibit glassy behavior, in which the ferroic degrees of freedom (magnetization, polarization, strain) exhibit a loss of long-range translational symmetry. A consequence of this loss of long-range symmetry is the suppression of the ferroic phase transitions. Moreover, these unique glassy systems exhibit dynamic and thermodynamic behavior analogous to regular structural glasses. Conventionally, the onset of glassy behavior is brought about by the introduction of spatial heterogeneities, typically originating from point defects, particularly in the case of strain glasses. Here, we demonstrate, for the first time, that configurational order/disorder in a single ferromagnetic alloy (Ni45Co5Mn36.6In13.4) can be used to stabilize both strain and magnetic glasses. The control of the degree of configurational order – through simple heat treatment schedules –, and simultaneous application of stress and magnetic field enabled us to observe a Kauzmann point, that is, the collapse of the entropy difference between a crystalline and a glassy phase. Systematic investigation of the transformation behavior in this system as a function of heat treatment enabled us to observe four kinds of solid–solid phase transitions (ferromagnetic–paramagnetic, martensitic transformation, strain and magnetic glass) in a single composition. The alloy investigated can be used to further elucidate the nature of ferroic glass transitions and their coupling.

ChemInform Abstract: A Spin Glass Perspective on Ferroic Glasses

AbstractReview: 98 refs.

A long road to a bright future

A long road to a bright future

A long road to a bright future

physica status solidi (RRL) – Rapid Research LettersVolume 9, Issue 1 p. 1-2 Editorial A long road to a bright future First published: 21 January 2015 https://doi.org/10.1002/pssr.201570604Citations: 3AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Abstract Dear pss readers, “This year's Nobel Prize in Physics recognizes the pioneering work of Professors Isamu Akasaki, Hiroshi Amano and Shuji Nakamura for the breakthrough developments in GaN materials and devices that enabled the field of solid state lighting. Blue LEDs have revolutionized display technology and enabled high efficiency white light sources.” said our Editorial Advisory Board member Jim Speck in response to our enthusiastic congratulations to his colleague at University of California, Santa Barbara. It was certainly an exceptional moment for a journal that has extensively documented GaN-related research for decades. Isamu Akasaki and Hiroshi Amano, then both Meijo University and Nagoya University, published in pss on dislocations and stress in AlGaN/GaN thin films, e.g. [1, 2], Hiroshi Amano repeatedly acted as a guest editor [3–5], and all three laureates together have more than a 150 articles in pss and continue to publish on the topic. Obviously, though these contributions have gathered more than 1400 citations to date, not all are “breakthroughs”. Most are documenting continuous achievements in an important and highly specialized area. But together they witness the exceptional persistence required to master the growth of GaN to the degree of perfection that enabled blue LEDs. It is an example for the amount of patient, high-level work that is necessary to turn a brilliant idea into a widespread invention, and pss is proud to accompany such progress along the way. Regarding today's promising trends in materials physics, we would like to showcase some of the special issues and topical sections that appeared in pss sister journals in 2014: “Oxide materials might form the basis for the next technological revolutions” according to J. M. Knaup, T. Frauenheim, P. Broqvist, and S. Ramanathan, the guest editors of the pss (RRL) Focus issue “Functional Oxides” [6]. These materials' enhanced complexity proposes both a greater challenge and greater benefits for future electronics and energy applications, and the 3 Reviews and 20 Letters offer computational and experimental perspectives on the current understanding. A topical section “Nanoscaled Magnetism and Applications”, guest-edited by A. Zhukov, features contributions on magnetocaloric materials, spin relaxation, magnetization processes and magnetic nanostructures in pss (a) [7]. Another bustling topic in pss (a) are the recurring annual diamond and nanocarbon special issues, this time focused on “Advances on Diamond Surfaces and Devices” edited by B. Rezek, M. Nesládek, and K. Haenen [8], and kicked-off by a Feature Article “Photoelectron emission from lithiated diamond” by K. M. O'Donnell, L. Ley, and others [9]. The logo of our journal assembled with blue GaN-on-Si LEDs (courtesy of Armin Dadgar, Otto-von Guericke-Universität, Magdeburg, Germany) pss (b) ventured on new grounds of theoretical method development: “Computational Thermo¬dynamics” is a joint effort of scientists from the density functional theory and CALPHAD user communities to pave the way to a connection of these two approaches of materials description. The extended Preface by T. Hickel, U. R. Kattner, and S. G. Fries and five Feature Articles ([10] and references therein) have been ranking among the most accessed articles of pss (b) ever since January. P. Entel et al. propose a promising perspective on materials in the Special Issue “Ferroic Glasses: Magnetic, Polar and Strain Glass”, comprising 21 contributions [11]. A core topic for pss is discussed in the Feature Article “Zinc oxide – From dilute magnetic doping to spin transport” by M. Opel et al. [12], which is part of the Special Issue “Semiconductor Spintronics” guest-edited by M. Oestreich and J. König [13]. The presentation of this and other great content in pss is possible only with the dedicated work of our editors, authors, and reviewers. Let us take the opportunity to say: Thank you. Looking to the near future we are delighted to welcome new members to the Editorial Advisory Board: Zexian Cao (Institute of Physics, Chinese Academy of Sciences, Beijing), Claudia Felser (Max Planck Institute for Chemical Physics of Solids, Dresden, Germany), Marius Grundmann (Universität Leipzig, Germany), Ken Haenen (Universiteit Hasselt, Belgium), and S. N. Piramanayagam (A*STAR, Singapore) have agreed to join. We are much looking forward to their help and support with further strengthening pss bonds to the scientific community worldwide. With best wishes, Sabine Bahrs and Stefan Hildebrandt Citing Literature Volume9, Issue1January 2015Pages 1-2 RelatedInformation

A long road to a bright future

AbstractDear pss readers,“This year's Nobel Prize in Physics recognizes the pioneering work of Professors Isamu Akasaki, Hiroshi Amano and Shuji Nakamura for the breakthrough developments in GaN materials and devices that enabled the field of solid state lighting. Blue LEDs have revolutionized display technology and enabled high efficiency white light sources.” said our Editorial Advisory Board member Jim Speck in response to our enthusiastic congratulations to his colleague at University of California, Santa Barbara. It was certainly an exceptional moment for a journal that has extensively documented GaN‐related research for decades. Isamu Akasaki and Hiroshi Amano, then both Meijo University and Nagoya University, published in pss on dislocations and stress in AlGaN/GaN thin films, e.g. [1, 2], Hiroshi Amano repeatedly acted as a guest editor [3–5], and all three laureates together have more than a 150 articles in pss and continue to publish on the topic. Obviously, though these contributions have gathered more than 1400 citations to date, not all are “breakthroughs”. Most are documenting continuous achievements in an important and highly specialized area. But together they witness the exceptional persistence required to master the growth of GaN to the degree of perfection that enabled blue LEDs. It is an example for the amount of patient, high‐level work that is necessary to turn a brilliant idea into a widespread invention, and pss is proud to accompany such progress along the way.Regarding today's promising trends in materials physics, we would like to showcase some of the special issues and topical sections that appeared in pss sister journals in 2014:“Oxide materials might form the basis for the next technological revolutions” according to J. M. Knaup, T. Frauenheim, P. Broqvist, and S. Ramanathan, the guest editors of the pss (RRL) Focus issue “Functional Oxides” [6]. These materials' enhanced complexity proposes both a greater challenge and greater benefits for future electronics and energy applications, and the 3 Reviews and 20 Letters offer computational and experimental perspectives on the current understanding.A topical section “Nanoscaled Magnetism and Applications”, guest‐edited by A. Zhukov, features contributions on magnetocaloric materials, spin relaxation, magnetization processes and magnetic nanostructures in pss (a) [7]. Another bustling topic in pss (a) are the recurring annual diamond andmagnified imageThe logo of our journal assembled with blue GaN‐on‐Si LEDs (courtesy of Armin Dadgar, Otto‐von Guericke‐Universität, Magdeburg, Germany)nanocarbon special issues, this time focused on “Advances on Diamond Surfaces and Devices” edited by B. Rezek, M. Nesládek, and K. Haenen [8], and kicked‐off by a Feature Article “Photoelectron emission from lithiated diamond” by K. M. O'Donnell, L. Ley, and others [9].pss (b) ventured on new grounds of theoretical method development: “Computational Thermodynamics” is a joint effort of scientists from the density functional theory and CALPHAD user communities to pave the way to a connection of these two approaches of materials description. The extended Preface by T. Hickel, U. R. Kattner, and S. G. Fries and five Feature Articles ([10] and references therein) have been ranking among the most accessed articles of pss (b) ever since January.P. Entel et al. propose a promising perspective on materials in the Special Issue “Ferroic Glasses: Magnetic, Polar and Strain Glass”, comprising 21 contributions [11]. A core topic for pss is discussed in the Feature Article “Zinc oxide – From dilute magnetic doping to spin transport” by M. Opel et al. [12], which is part of the Special Issue “Semiconductor Spintronics” guest‐edited by M. Oestreich and J. König [13].The presentation of this and other great content in pss is possible only with the dedicated work of our editors, authors, and reviewers. Let us take the opportunity to say: Thank you.Looking to the near future we are delighted to welcome new members to the Editorial Advisory Board:Zexian Cao (Institute of Physics, Chinese Academy of Sciences, Beijing), Claudia Felser (Max Planck Institute for Chemical Physics of Solids, Dresden, Germany), Marius Grundmann (Universität Leipzig, Germany), Ken Haenen (Universiteit Hasselt, Belgium), and S. N. Piramanayagam (A*STAR, Singapore) have agreed to join. We are much looking forward to their help and support with further strengthening pss bonds to the scientific community worldwide.With best wishes,Sabine Bahrs and Stefan Hildebrandt

A long road to a bright future

Dear pss readers, “This year's Nobel Prize in Physics recognizes the pioneering work of Professors Isamu Akasaki, Hiroshi Amano and Shuji Nakamura for the breakthrough developments in GaN materials and devices that enabled the field of solid state lighting. Blue LEDs have revolutionized display technology and enabled high efficiency white light sources.” said our Editorial Advisory Board member Jim Speck in response to our enthusiastic congratulations to his colleague at University of California, Santa Barbara. It was certainly an exceptional moment for a journal that has extensively documented GaN-related research for decades. Isamu Akasaki and Hiroshi Amano, then both Meijo University and Nagoya University, published in pss on dislocations and stress in AlGaN/GaN thin films, e.g. 1, 2, Hiroshi Amano repeatedly acted as a guest editor 3-5, and all three laureates together have more than a 150 articles in pss and continue to publish on the topic. Obviously, though these contributions have gathered more than 1400 citations to date, not all are “breakthroughs”. Most are documenting continuous achievements in an important and highly specialized area. But together they witness the exceptional persistence required to master the growth of GaN to the degree of perfection that enabled blue LEDs. It is an example for the amount of patient, high-level work that is necessary to turn a brilliant idea into a widespread invention, and pss is proud to accompany such progress along the way. Regarding today's promising trends in materials physics, we would like to showcase some of the special issues and topical sections that appeared in pss sister journals in 2014: “Oxide materials might form the basis for the next technological revolutions” according to J. M. Knaup, T. Frauenheim, P. Broqvist, and S. Ramanathan, the guest editors of the pss (RRL) Focus issue “Functional Oxides” 6. These materials' enhanced complexity proposes both a greater challenge and greater benefits for future electronics and energy applications, and the 3 Reviews and 20 Letters offer computational and experimental perspectives on the current understanding. The logo of our journal assembled with blue GaN-on-Si LEDs (courtesy of Armin Dadgar, Otto-von Guericke-Universität, Magdeburg, Germany) A topical section “Nanoscaled Magnetism and Applications”, guest-edited by A. Zhukov, features contributions on magnetocaloric materials, spin relaxation, magnetization processes and magnetic nanostructures in pss (a) 7. Another bustling topic in pss (a) are the recurring annual diamond and nanocarbon special issues, this time focused on “Advances on Diamond Surfaces and Devices” edited by B. Rezek, M. Nesládek, and K. Haenen 8, and kicked-off by a Feature Article “Photoelectron emission from lithiated diamond” by K. M. O'Donnell, L. Ley, and others 9. pss (b) ventured on new grounds of theoretical method development: “Computational Thermodynamics” is a joint effort of scientists from the density functional theory and CALPHAD user communities to pave the way to a connection of these two approaches of materials description. The extended Preface by T. Hickel, U. R. Kattner, and S. G. Fries and five Feature Articles (10 and references therein) have been ranking among the most accessed articles of pss (b) ever since January. P. Entel et al. propose a promising perspective on materials in the Special Issue “Ferroic Glasses: Magnetic, Polar and Strain Glass”, comprising 21 contributions 11. A core topic for pss is discussed in the Feature Article “Zinc oxide – From dilute magnetic doping to spin transport” by M. Opel et al. 12, which is part of the Special Issue “Semiconductor Spintronics” guest-edited by M. Oestreich and J. König 13. The presentation of this and other great content in pss is possible only with the dedicated work of our editors, authors, and reviewers. Let us take the opportunity to say: Thank you. Looking to the near future we are delighted to welcome new members to the Editorial Advisory Board: Zexian Cao (Institute of Physics, Chinese Academy of Sciences, Beijing), Claudia Felser (Max Planck Institute for Chemical Physics of Solids, Dresden, Germany), Marius Grundmann (Universität Leipzig, Germany), Ken Haenen (Universiteit Hasselt, Belgium), and S. N. Piramanayagam (A*STAR, Singapore) have agreed to join. We are much looking forward to their help and support with further strengthening pss bonds to the scientific community worldwide. With best wishes,Sabine Bahrs and Stefan Hildebrandt

Ferroic Glasses: Magnetic, Polar and Strain Glass

When a liquid phase is cooled below its freezing temperature, it usually transforms to a crystalline solid where the disorder-order transition is driven by the thermodynamic requirement of reducing the entropy in the corresponding thermodynamic potential of the system. However, some liquids do not crystallize because of the complex nature of the inter-atomic interactions as, for example, in multi-atom metallic materials when heterogeneous nucleation can be reduced during cooling from the liquid to the solid phase, which can be influenced by strain rates modifying the viscosity 1, 2. The resulting non-crystalline materials show a complex potential-energy landscape and the elastic properties of a cluster of atoms can vary significantly in space. Such local properties of metallic glasses are still subject of intensive ongoing research 3. But glass formation is also possible in a variety of other materials where the high-temperature state with chemical disorder of the atoms can freeze into a statically disordered phase showing local order. This is possible in martensitically transforming alloys. In such alloys the premartensitic region at temperatures above the martensitic transformation temperature is often subject to so-called tweed effects, which can be considered to arise from dynamically disordered lattice strains 4. These disordered lattice strains may arise from the compositional (chemical) disorder of the material or from doping the materials with additional point defects. Both effects can be thought to be responsible for the appearance of these ‘dynamically disordered lattice strains’, which below a critical temperature and above a critical degree of disorder or above a critical concentration of point defects may transform to a frozen disordered strain state, a so-called ‘strain glass’. Such strain glasses have recently been observed in some intermetallic Ni-Ti-Fe and Ni-Co-Mn-Ga Heusler alloys 5, 6. The experimental evidence of the non-ergodic behavior of these ‘new glasses’ comes from measuring ‘field-cooled- field-heated’ and ‘zero-field-cooled-zero-field-heated’ curves over the glass formation temperature down to low temperatures. Very early such non-ergodic behavior has already been observed in some relaxor ferroelectrics which show the effect of a polarization glass 7. The idea can be pursued to include besides the ferroelastic systems also magnetic metals with ferromangetic-antiferromagnetic interactions and chemical disorder giving rise to usual spin glass or cluster-spin glass phases. Famous examples are here the recently discovered Ni-Co-Mn-(In, Sn) intermetallics 8, 9. In this special issue we present a series of experimental and theoretical articles which deal with various and important physical aspects of such alloys in this new and exciting field of ‘strain glasses’ including articles with a discussion of the influence of magnetism on the glassy features. Of particular interest is that in some of these new materials we find both effects simultaneously, namely, the interaction of strain glass and cluster-spin glass formation. We expect that this rather new emerging field of ‘strain glasses’ in martensitically transforming alloys and the generalization of this concept to include other glass formation tendencies as in disordered ferroelectrics and disordered magnetic systems will attract many readers and might lead to a lot of activities in near future. Last not least we would like to mention that most alloys which are discussed in the different contributions to this special issue are smart materials showing shape-memory effects and magnetocaloric properties to name only two properties of technological relevance. It may turn out that ‘for the fi rst time’ glassy features of metals may be benefi cial for technologically relevant smart materials. In the due course and making of this special issue on fundamental research related to the new phases of ferroic glasses which appear now as well-established exciting experimental and theoretical observation in various martensites, ferroelectrics and other ferroic materials, the Guest Editor (P.E.) would like to thank the DFG Priority Programme "Change of microstructure and shape of solid materials by external magnetic fi elds" (SPP 1239, Dr. Sebastian Fähler, Chair) as well as the German multinational conglomerate Thyssen- Krupp Steel Europe AG (Klaus Bailer, Senior Vice President, Human Resources) for financial support. The Editors, Peter Entel, Raymundo Arroyave, Sebastian Fähler, Ryosuke Kainuma, Antoni Planes, Xiaobing Ren, and Avadh Saxena

Strain glass and ferroic glass – Unusual properties from glassy nano‐domains

The present article serves as a concise review of strain glass and its broader concept – ferroic glass. Strain glass is a frozen disordered strain state composed of nano‐sized strain domains, which is formed due to the frustration created by point defects or dopants. Such frustration creates glassy nano‐sized martensite‐like domains that do not grow into a macroscopic martensite during cooling and instead show typical glass‐freezing dynamics. Strain glass bears much resemblance with the glass phenomena found in other two types of ferroic systems, relaxor ferroelectric, and spin glass. These three ferroics‐based glasses are thus called ferroic glasses. Characteristics of strain glass, including recent in situ high‐resolution TEM images, are shown. Unusual properties associated with strain glass, such as superelasticity with narrow hysteresis, high‐damping, and low modulus, as well as Invar and Elinvar effect in cold‐rolled β‐Ti alloys are demonstrated.