Magnetic Lattice Research Articles

Structural stabilities and natural half-metallic properties of OsXCoSi (X=Ti, Zr, Hf) quaternary Heusler alloys series first-principles calculations

Based on first-principles calculation of density functional theory, this study investigates the structural stability, magnetic properties, and electronic properties of the three different phases (i.e. type 1, type 2, and type 3) of OsXCoSi (X=Ti, Zr, Hf) in a new quaternary Heusler alloy series. The corresponding equilibrium lattice constants of each type are optimized, and the change of formation enthalpy and elastic constant phonon spectrum show that the OsXCoSi (X=Ti, Zr, Hf) alloy is thermodynamically, dynamically and mechanically stable. Furthermore, the bonding features of each phase are discussed. It is found that all type 1 structures of OsXCoSi (X=Ti, Zr, Hf) exhibit natural half-metallicity (HM) in equilibrium lattice constant, and their equilibrium lattice constants in the ground state were determined to be 5.909 Å for OsTiCoSi, 6.155 Å for OsZrCoSi, and 6.100 Å for OsHfCoSi. Meanwhile, by testing the alloy under different pressures, the range of the integer magnetic moment non-equilibrium lattice constants for the three alloys OsTiCoSi, OsZrCoSi, and OsHfCoSi are 5.710 Å ∼ 6.329 Å, 5.696 Å ∼ 6.1557 Å and 5.716 Å ∼6.1009 Å, respectively, which is wide and is more close to the practical application for spin-polarized materials. In addition, its magnetic moment is consistent with the values given by the Slater–Pauling rule. Furthermore, the forming of the HM gap is examined by analysing the total and partial density of states, energy bands of alloy’s electronic property, with respect to the calculated results. What’s more, special attention is paid to the differences of the properties for series Heusler alloys. It is found that the electronics properties distinction is mainly based on valence electron changes. However, the lattice constants are susceptible to size of a nucleus.

Nonvolatile Multistate Manipulation of Topological Magnetism in Monolayer CrI3 through Quadruple-Well Ferroelectric Materials.

Nonvolatile multistate manipulation of two-dimensional (2D) magnetic materials holds promise for low dissipation, highly integrated, and versatile spintronic devices. Here, utilizing density functional theory calculations and Monte Carlo simulations, we report the realization of nonvolatile and multistate control of topological magnetism in monolayer CrI3 by constructing multiferroic heterojunctions with quadruple-well ferroelectric (FE) materials. The Pt2Sn2Te6/CrI3 heterojunction exhibits multiple magnetic phases upon modulating FE polarization states of FE layers and interlayer sliding. These magnetic phases include Bloch-type skyrmions and ferromagnetism, as well as a newly discovered topological magnetic structure. We reveal that the Dzyaloshinskii-Moriya interaction (DMI) induced by interfacial coupling plays a crucial role in magnetic skyrmion manipulation, which aligns with the Fert-Levy mechanism. Moreover, a regular magnetic skyrmion lattice survives when removing a magnetic field, demonstrating its robustness. The work sheds light on an effective approach to nonvolatile and multistate control of 2D magnetic materials.

Perfect Absorption with Independent Electric and Magnetic Lattice Resonances in Metallo‐Dielectric Arrays

AbstractLattice resonances are collective modes supported by periodic arrays of nanostructures. They originate from the coherent interaction between the localized modes of the individual constituents of the array, which, for systems made of metallic nanostructures, usually correspond to the electric dipole plasmon. Unfortunately, fundamental symmetry reasons preclude a two‐dimensional (2D) arrangement of electric dipoles from absorbing more than half the incident power, thus imposing a strong limitation on the performance of conventional lattice resonances. This work introduces an innovative solution to overcome this constraint, which is based on using an array made of a unit cell containing one metallic and one dielectric nanostructure. Using a rigorous coupled dipole model, it is shown that this system can support two independent lattice resonances associated, respectively, with the electric and magnetic dipole modes of the nanostructures. By adjusting the geometrical characteristics of the array, these two lattice resonances can be meticulously aligned in the spectral domain, leading to the total absorption of the incident power. The results of this work provide clear, yet general, guidelines for the rational design of arrays sustaining lattice resonances capable of producing perfect absorption, thus leveraging the potential of these modes for applications requiring an efficient absorption of light.

Probing the Sense of Spin Twisting in Magnetic Skyrmion Lattice by Resonant X-ray Scattering

Probing the Sense of Spin Twisting in Magnetic Skyrmion Lattice by Resonant X-ray Scattering

Uncertainty quantification of phase transitions in magnetic materials lattices

This Perspective article aims to emphasize the crucial role of uncertainty quantification (UQ) in understanding magnetic phase transitions, which are pivotal in various applications, especially in the transportation and energy sectors [D. C. Jiles, Acta Mater. 51, 5907–5939 (2003) and Gutfleisch et al., Adv. Mater. 23, 821–842 (2011)]. Magnetic materials undergoing phase transitions, particularly due to high temperatures, pose challenges related to the loss of their inherent properties. However, pinpointing a definitive phase transition temperature proves challenging due to the diverse and uncertain nanostructure of materials. Deterministic approaches are limited when seeking a precise threshold. As a result, there is a need to develop probabilistic methods to improve the understanding of this physical problem. In this study, UQ is explored within the context of magnetic phase transitions. In addition, the broader applications of UQ in relation to microstructures and Hamiltonian systems are discussed to highlight its significance in materials science. Furthermore, this study discusses the potential future work on the integration of quantum computing to achieve more efficient UQ solutions of magnetic phase transitions using Ising models.

Unification of Spin Helicity in the Magnetic Skyrmion Lattice of EuNiGe3

In the magnetic skyrmion lattice of non-centrosymmetric EuNiGe3, the original magnetic helicity, determined by the antisymmetric exchange interaction, is reversed, resulting in a unified helicity.

Atypical breathing driven two-dimensional valley multiferroicity.

Valley multiferroicity, coupled with ferro-valleytricity and primary ferroicities in a single phase, is of fundamental significance in condensed-matter physics and materials science, as it provides a convenient route to reverse the anomalous valley Hall (AVH) effect. Current research in this field focuses mainly on ferromagnetic ferro-valleytricity, whereas ferroelectric ferro-valleytricity is seldom explored. Here, using symmetry arguments and tight-binding model analysis, we report a novel mechanism of coupling ferro-valleytricity with ferroelectricity, i.e., single-phase valley multiferroicity, in a two-dimensional magnetic lattice. This mechanism correlates to the atypical breathing nature of the magnetic lattice. Importantly, the valley physics, associated with Berry curvature, can be reversed under a ferroelectric transition, thereby guaranteeing the ferroelectrically reversible AVH effect. The underlying physics are discussed in detail. Based on first-principles calculations, we further confirm valley multiferroicity in a real 2D magnetic material of single-layer Gd2CO2. The explored phenomena and mechanism are not only useful for fundamental research in valley multiferroics but also enable a wide range of applications in nanodevices.

Elettra 2.0: The Vacuum System Design for a New Generation Storage Ring

Next-generation synchrotron facilities currently under development and construction are promising and delivering great advances in terms of machine design and research physics. At the same time, they are pushing the limits of technological solutions for various subsystems: to achieve the desired ultra-low electron beam emittance required in the next generation machines, the magnetic lattice has to adopt a compact design with reduced magnet apertures and other constraints like high heat load from synchrotron radiation, dynamic pressure inside vacuum chambers and chamber wall impedance are presenting unique challenges for the vacuum and engineering teams. At Elettra-Sincrotrone Trieste (Italy), the Elettra 2.0 project aims to develop a new-generation storage ring. Taking into consideration the above-mentioned constraints, we decided to adopt a new design of a vacuum chamber, while utilizing novel pumping solutions to overcome hugely reduced conductance compared to the current machine. Large sputter ion pumps (SIP) will be in the majority replaced by distributed non-evaporable getter (NEG) coatings and small NEG cartridges and SIP pumps. For the synchrotron radiation handling, due to the tight space constraints imposed by the compact lattice, the photon absorption will be managed jointly with discrete and distributed solutions: photon absorbers have been carefully studied for combining compact form and high power density loads, while key sections of the new storage ring will be water-cooled. Throughout the whole development phase, we were using Monte-Carlo simulation codes like SynRad and MolFlow+ as effective tools supporting the design of new vacuum chambers and photon absorbers. The current state of development for the Elettra 2.0 vacuum system, the challenges we faced and the solutions we adopted are presented here.

Evidence of zero group velocity at the lowest dispersion branch through local interactions

Zero group velocity (ZGV) modes can be utilized in many applications in both optics and acoustics. There exist numerous realizations of metamaterials with ZGVs at higher dispersion branches. However, to engineer the lowest dispersion branch to retain ZGVs, non-local metamaterials with couplings beyond the nearest neighbor are usually at play (i.e., roton-like dispersion). To date, there exists no realization of roton-like dispersion for the lowest branch without non-local couplings. Non-locality, while rich in dynamics, can render designs rather complex. Here, we provide the first experimental evidence of a ZGV point for the lowest dispersion branch within the first Brillouin zone with local interactions. We utilize nonlinear magnetic lattices as a platform to sculpt our dispersion. Our findings might enable the realization of exotic metamaterials with simple designs.

Antiferromagnetic imaging via ptychographic phase retrieval

Antiferromagnetic imaging is critical for understanding and optimizing the properties of antiferromagnetic materials and devices. Despite the widespread use of high-energy electrons for atomic-scale imaging, they have low sensitivity to spin textures. Typically, the magnetic contribution to the phase of a high-energy electron wave is weaker than one percent of the electrostatic potential. Here, we demonstrate direct imaging of antiferromagnetic lattice through precise phase retrieval via electron ptychography, paving the way for magnetic lattice imaging of antiferromagnetic materials and devices.

The ground state, localization, and chiral edge dynamics of a three-legged bosonic magnetic ladder

Three-legged bosonic/fermionic magnetic ladder, reproducing the main features of magnetic lattice systems, is an ideal model to study the edge-bulk coupling and chiral edge dynamics, which are a hallmark of quantum Hall physics. Here, the ground state transition, localization, and chiral edge (bulk) states of an interacting three-legged bosonic magnetic ladder are studied analytically and numerically. When the system is in a quasi-steady state, using variational analysis, the threshold for the transition from zero momentum state to plane wave state is obtained. The energy spectrum, the ground state diagram, the chiral current of the system are presented, and the chiral current reversal at the state transition point is observed. Furthermore, the localization and its stability in the system are discussed, and rich localized phenomena (diffusion, breather, soliton, and self-trapping) are predicted. Stable soliton/breather prefers to form an edge state, while the self-trapping is favorite to form a bulk state, i.e. localized edge and bulk states are obtained. Particularly, for the unstable soliton in the ground state or metastable state, different kinds of chiral edge/bulk state and edge-bulk coupling are observed. The stability of the localized states, the edge-bulk coupling characteristics, and the chirality of the system depend on the energy band structure of the system. Additionally, a controllable transition between localized edge state and bulk state is realized by quenching the soliton state. We proposed a theoretical evidence to design and manipulate edge-bulk coupling and different kinds of localized/chiral edge (bulk) states in three-legged bosonic magnetic ladder.

Lattice Mie resonances and emissivity enhancement in mid-infrared iron pyrite metasurfaces.

High-refractive-index antennas with characteristic dimensions comparable to wavelength have a remarkable ability to support pronounces electric and magnetic dipole resonances. Furthermore, periodic arrangements of such resonant antennas result in narrow and strong lattice resonances facilitated by the lattice. We design iron pyrite antennas operating in the mid-infrared spectral range due to the material's low-energy bandgap and high refractive index. We utilize Kirchhoff's law, stating that emissivity and absorptance are equal to each other in equilibrium, and we apply it to improve the thermal properties of the iron pyrite metasurface. Through the excitation of collective resonances and manipulation of the antenna lattice's period, we demonstrate our capacity to control emissivity peaks. These peaks stem from the resonant excitation of electric and magnetic dipoles within proximity to the Rayleigh anomalies. In the lattice of truncated-cone antennas, we observe Rabi splitting of electric and magnetic dipole lattice resonances originating from the antennas' broken symmetry. We demonstrate that the truncated-cone antenna lattices support strong out-of-plane magnetic dipole lattice resonances at oblique incidence. We show that the truncated-cone antennas, as opposed to disks or cones, facilitate a particularly strong resonance and bound state in the continuum at the normal incidence. Our work demonstrates the effective manipulation of emissivity peaks in iron pyrite metasurfaces through controlled lattice resonances and antenna design, offering promising avenues for mid-infrared spectral engineering.

Anisotropic microwave response in Cr1∕3TaS2 hosting chiral magnetic soliton

Chromium-intercalated hexagonal Cr1∕3TaS2 possesses exotic properties, such as high-temperature magnetic soliton, crossover of critical behavior, and nontrivial magnetism. In this study, we employ the electron spin resonance (ESR) technique to modulate and study the chiral magnetic soliton lattice (CSL) in Cr1∕3TaS2 using microwave at X-band. The experimental results show that Cr1∕3TaS2 has a particularly strong microwave response when H⊥c but very weak feedback when H//c, revealing an anisotropic microwave response. When H⊥c, the resonance peak at lower fields results from the surface barrier induced by the competition between Dzyaloshinsky–Moriya interaction, Zeeman energy, and exchange energy. The dominant resonance is caused by the ferromagnetic mode with the twisted region as the boundary condition, which transforms into a paramagnetic resonance above the phase transition temperature (TC). Furthermore, an unusual temperature dependence of ESR spectra is revealed. The crystalline electric field (CEF) excitation owing to large strong spin–orbit coupling results in the widening of the ESR linewidth above TC. Furthermore, an abrupt shift in the resonance field Hr2 and ESR linewidth ΔHPP2 is observed around TC, which is attributed to a sudden change in spin-exchange interactions and magnetic anisotropy around TC, as Cr1∕3TaS2 was previously observed for spin interaction transition from strong anisotropic 3D-Ising type to isotropic 3D-Heisenberg magnetic interaction below TC. This work demonstrates that the ESR can detect the CSL state and investigate materials with nontrivial magnetism.

Jahn–Teller Magnets

A wide class of materials with different crystal and electronic structures including quasi-2D unconventional superconductors, such as cuprates, nickelates, ferropnictides/chalcogenides, ruthenate Sr2RuO4, and 3D systems, such as manganites RMnO3, ferrates (CaSr)FeO3, nickelates RNiO3, silver oxide AgO, are based on Jahn–Teller 3d and 4d ions. These unusual materials, called Jahn–Teller (JT) magnets, are characterized by an extremely rich variety of phase states, spanning from non-magnetic and magnetic insulators to unusual metallic and superconducting states. The unconventional properties of JT magnets can be attributed to the instability of their highly symmetric Jahn–Teller “progenitors” with the ground orbital E-state with repect to charge transfer, anti-Jahn–Teller d-d disproportionation, and the formation of a system of effective local composite spin–singlet or spin–triplet, electronic, or hole S-type bosons moving in a non-magnetic or magnetic lattice. We consider specific features of the anti-JT-disproportionation reaction, properties of the electron–hole dimers, possible phase states and effective Hamiltonians for single- and two-band JT magnets, concluding with a short overview of physical properties for actual JT magnets.

Tetrahalidocuprate(II) complexes with substituted pyridinium ions: effects of halide substitution

The Cu(II) complexes (H-5-FAP)2CuBr4 (1) and (H-2,3-dimpy)2CuCl4 (2) have been prepared and characterized structurally and magnetically (H-5-FAP = 2-amino-5-fluoropyridinium; H-2,3-dimpy = 2,3-dimethylpyridinium). They crystallize in the space groups P-1 and Pbcn, respectively, in comparison to their halido counterparts (H-5-FAP)2CuCl4 (1a) and (H-2,3-dimpy)2CuBr4 (2a) which crystallize in the space groups P21/c and P21/n. The differences in crystal packing, resulting in part from the difference in distortion of the CuX4 2− ions, create different magnetic lattices. Data for 1 were fit to the strong-rail ladder model resulting in a Curie constant of 0.400(8) emu-K/mol-Oe, J/kB-rail = −5.77(1) K and J/kB-rung = 3.17(3) K. Data for 2 were fit to the Curie-Weiss law resulting in a Curie constant of 0.398(1) emu-K/mol-Oe and θ = −0.11(4) K, indicating a virtual lack of magnetic exchange interactions. The structures and magnetic properties are compared to literature compounds and general trends noted. The differences in the chloride/bromide ions in the structure lead to significant differences in the packing in the cases of both 1 and 2, which result in differences in the antiferromagnetic exchange in both complexes and, in the case of 2, versus 2a, an elimination of the antiferromagnetic properties.

Spin Frustration in Organic Radicals.

Spin frustration, which results from geometric frustration and a systematical inability to satisfy all antiferromagnetic (AF) interactions between unpaired spins simultaneously, is under the spotlight for its importance in physics and materials science. Spin frustration is treated as the structural basis of quantum spin liquids (QSLs). Featuring flexible chemical structures, organic radical species exhibit great potential in building spin-frustrated molecules and lattices. So far, the reported examples of spin-frustrated organic radical compounds include triradicals, tetrathiafulvalene (TTF) radicals and derivatives, [Pd(dmit)2 ] compounds (dmit=1,3-dithiol-2-thione-4,5-dithiolate), nitronyl nitroxides, fullerenes, polycyclic aromatic hydrocarbons (PAHs), and other heterocyclic compounds where the spin frustration is generated intra- or intermolecularly. In this Minireview, we provide a brief summary of the reported radical compounds that possess spin frustration. The related data, including magnetic exchange coupling parameters, spin models, frustration parameters, and crystal lattices, are summarized and discussed.

Spin Frustration in Organic Radicals

AbstractSpin frustration, which results from geometric frustration and a systematical inability to satisfy all antiferromagnetic (AF) interactions between unpaired spins simultaneously, is under the spotlight for its importance in physics and materials science. Spin frustration is treated as the structural basis of quantum spin liquids (QSLs). Featuring flexible chemical structures, organic radical species exhibit great potential in building spin‐frustrated molecules and lattices. So far, the reported examples of spin‐frustrated organic radical compounds include triradicals, tetrathiafulvalene (TTF) radicals and derivatives, [Pd(dmit)2] compounds (dmit=1,3‐dithiol‐2‐thione‐4,5‐dithiolate), nitronyl nitroxides, fullerenes, polycyclic aromatic hydrocarbons (PAHs), and other heterocyclic compounds where the spin frustration is generated intra‐ or intermolecularly. In this Minireview, we provide a brief summary of the reported radical compounds that possess spin frustration. The related data, including magnetic exchange coupling parameters, spin models, frustration parameters, and crystal lattices, are summarized and discussed.

Diode type unidirectional conduction in Hall measurement of magnetic honeycomb lattice

Artificial magnetic honeycomb lattice is emerging as a new platform for spintronics research applications, as evidenced from recent findings of magnetic diode effect and collective magnetic switching phenomena in different lattice geometries. In this report, we present Hall measurements on thermally tunable artificial magnetic honeycomb lattice. Experimental investigation using detailed Hall probe measurements reveals diode-type unidirectional conduction in both longitudinal and Hall resistances. The unidirectional conduction persists to low temperature but remains unaffected to modest application of perpendicular magnetic field. The behavior can be understood in terms of topological magnetic charges that arise on the vertices of honeycomb lattice and affect electrical transport properties. The experimental finding can be utilized for the design of spintronic logic devices.

Atomic order, magnetic and transport phenomena in half-Heusler CoMnSb0.9Z0.1 alloys (Z = Si, Al, Sn, and Bi)

In this study, we investigate the effects of doping with ∼10 at% of Si, Al, Sn, and Bi on the atomic order, microstructure, and magnetic properties of CoMnSb samples prepared using the arc-melting method. X-ray diffraction, scanning electron microscopy, and magnetometry techniques were employed to derive the structural and magnetic parameters. The samples demonstrate a superstructure with an Fm-3m space group. They exhibit a saturation moment of 3.71–4.71 μB per formula unit at 5 K and a Curie temperature ranging from 474 to 507 K. Rietveld refinement performed on the XRD data revealed a possible occupation of magnetic atoms in the vacant 32f (x’, x’, x’) sites and atomic swapping, both of which may affect the magnitudes of the magnetic moment and Curie temperature. The electrical measurement results show that the grain boundaries and voids govern the conductivity of the samples. The spin polarization of the Si-doped sample was determined based on the grain-boundary magnetoresistance effect, which showed that this sample has a high degree of atomic order, consistent with the low magnetic moment, Curie temperature, and lattice constant.

The Effect of Exchange Interaction on Phase Transition Behavior of Magnetic Nanotubes

In this paper, the phase diagram of the Blume-Capel model under exchange interaction between lattice points in different positions in magnetic nanotube lattice is studied with effective field theory. The research shows that the interaction between nearest neighbors and the lattice field strength strongly influences the system’s three critical points and phase transition temperature. Under certain conditions, there are three critical points in the system. That is, the relationship between the crucial points is linear from the second-order phase transition to the first-order phase transition. First-order phase transition replaces second-order phase transition in the system’s phase transition. The findings demonstrate that exchange interaction significantly affects the system’s phase transition, and they offer a theoretical framework for both industrial production and experimental study.