Magnetoelastic Effects Research Articles

Separation of Heating and Magnetoelastic Coupling Effects in Surface-Acoustic-Wave-Enhanced Creep of Magnetic Domain Walls

Separation of Heating and Magnetoelastic Coupling Effects in Surface-Acoustic-Wave-Enhanced Creep of Magnetic Domain Walls

Emergent evolution of first-order phase transitions from magneto-structural to magneto-elastic in MnCo1−y Fe y Ge1−x Si x alloys

The emergent evolution of first-order phase transitions from magneto-structural to magneto-elastic and magnetocaloric effect (MCE) have been investigated by X-ray diffraction, differential scanning calorimetry and magnetization measurements. Applying the isostructural alloying principle, the martensitic transition temperature (T M) increases effectively and the Curie temperatures of the two phases increase slightly by substituting the Si content (x). With an appropriate amount of Fe and Si content, an emergent first-order antiferromagnetic–ferromagnetic magnetoelastic transition with thermal hysteresis in the martensitic state occurs for MnCo0.7Fe0.3Ge1–x Si x (x = 0.15–0.40) alloys, which results from the decrease in the nearest-neighbor Mn–Mn distance. Moreover, the values of magnetic entropy change (ΔS M), refrigeration capacity (RC) and temperature-averaged entropy change (TEC, 10 K) with ΔH = 50 kOe reach −12.2 J kg−1 K−1, 112.8 J kg−1 and 11.4 J kg−1 K−1 for MnCo0.7Fe0.3Ge0.8Si0.2 undergoing the ferromagnetic magneto-structural transition in the Curie temperature window. The results facilitate the magnetocaloric/magnetoelastic performance and tunability of multiple phase states in a wider temperature range.

Visible-light controlled interfacial magnetoelectric coupling in SrRuO3/BaTiO3 heterostructure

Artificial multiferroics provide a tunable magnetoelastic and magnetoelectric coupling owing to the variety of combinations of ferroelectric and ferromagnetic layers, hence facilitate a better perspective for device applications such as magnetic field sensors and electric write magnetic -read memory devices. The intertwined physical properties can be controlled via external parameters such as electric field, temperature, and magnetic field. Here, we report an additional mode to manoeuvre the magnetoelastic and magnetoelectric coupling in an epitaxial SrRuO3/BaTiO3 multiferroic heterostructure using polarized visible light illumination. The light-induced ferroelastic (FE) domain wall motion in underlying BaTiO3 leads to photostriction and photodomain effects. Consequently, the change in the converse magnetoelastic effects leads to modify the magnetic properties of the above grown SrRuO3 layer. Besides this, we have observed a sharp and persistent changes in the SrRuO3/ BaTiO3 heterostructure, when the system is electrically biased owing to the change in the interfacial converse magnetoelectric coupling. Light controlled magnetization tunability in BaTiO3-based artificial multiferroic can open an alternate way for potential applications in several types of wireless devices and magnetic field sensors, electric write magnetic-read memory devices and other interesting optomechanical systems. Our findings in this context can be proven indeed as a novel prospective for opto-spintronics device applications.

Crack self-sensing capability of glass fiber reinforced polymer composites embedded with magnetostrictive fibers in mixed-mode bending

Glass fiber reinforced polymer (GFRP) composites integrated with sensors have received attention because the composite material can transmit information about the structural condition during operation. This study investigated the crack self-sensing capability of GFRP composites with magnetostrictive Fe–Co fibers under mixed-mode bending. The mixed-mode bending (MMB) test was performed using GFRP composites with a certain number of Fe–Co fibers introduced. Three different mixed-mode I/II ratios for MMB tests were selected and tested. The self-sensing capability of crack propagation was discussed by measuring the magnetic flux density induced by the inverse magnetostrictive effect using Hall probes. The GFRP composites with Fe–Co fibers fabricated in this study are a promising monitoring technology for non-contact sensing.

Working Stress Measurement of Prestressed Rebars Using the Magnetic Resonance Method

Prestressed rebars are usually used to apply vertical prestress to concrete to prevent web cracking. The reduction of working stress will affect the durability of the structure. However, the existing working stress detection methods for prestressed rebars still need to be improved. To monitor the working stress of rebars, a magnetic resonance sensor was introduced to carry out experimental research. The correlation between rebar stress and the sensor’s induced voltage was theoretically analyzed using the magnetoelastic effect and magnetic resonance theory. A working stress monitoring method for prestressed rebars based on magnetic resonance was proposed. Working stress monitoring experiments were carried out for 16 mm, 18 mm, and 20 mm diameter rebars. The results showed that the induced voltage peak-to-peak value and the rebar prestress were nonlinearly correlated under different working conditions. Correlations between the characteristic indicators and the rebar working stress were obtained using nonlinear and linear fit. The cubic polynomial segmented fit outperformed the gradient overall linear fit, with the goodness of fit R2 greater than 0.96. The average relative error values of working stress monitoring were less than 5% under different working conditions. This provides a new method for working stress measurement of vertical prestressed rebars.

Large tunnel magnetoresistance in magnetic tunnel junctions with magnetic electrodes of metastable body-centered cubic CoMnFe alloys

A magnetic tunnel junction (MTJ) is a key device in spintronics applications, such as magnetoresistive random access memory (MRAM). Current standard magnetic material for MTJs is a body-centered cubic (bcc) FeCo(B), which shows large tunnel magnetoresistance (TMR) and high perpendicular magnetic anisotropy (PMA), both are crucial for high-memory capacities MRAM. It is demanded that magnetic materials showing TMR as well as PMA higher than FeCo(B) for further advance. One of alternative magnetic materials may be bcc Co since past ab-initio studies predict that bcc Co show large TMR effect in MgO-barrier MTJs and large PMA due to magneto-elastic effect for those strained state. However, bcc Co is thermodynamically unstable; thus, it is aimed to explore metastable bcc Co based alloys with high stability. Here, we propose metastable bcc Co based alloy with adding both Mn and Fe as a candidate. We study in-plane magnetized MTJs utilizing metastable bcc CoMnFe films as electrodes and demonstrate large TMR effect of 350% at 300 K and of 1002% at 5 K. This experimental finding will open a route to advanced bcc Co based magnetic material for MRAM applications.

Interlayer coupling-dependent magnetoelastic response in synthetic antiferromagnets

In recent years, antiferromagnetic materials have been attracting increasing interest for their stability in high magnetic fields and ultrafast magnetization dynamics. Since the energy scale of an interlayer exchange coupling (IEC) in a synthetic antiferromagnet (SAF) consisting of ferromagnetic/nonmagnetic/ferromagnetic multilayers is relatively smaller than that of an exchange coupling in antiferromagnetic materials, magnetic ordering of a SAF can be potentially controlled by an electric field, which is promising for energy-saving spintronic memory devices. However, an electric field-induced magnetoelastic response of SAFs on ferroelectric materials has not been sufficiently understood due to the presence of IEC that complicates magnetization dynamics. In this study, we prepare Co/Ru/Co SAFs with various amplitude of IEC on ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 substrates and systematically investigate their electric field-induced magnetoelastic response. We demonstrate that the magnetoelastic response disappears at the boundary where a switching between the antiferromagnetic and ferromagnetic IEC coupling occurs. The result provides insight into the coupling of the magnetoelastic effect and IEC and is useful in designing spintronic memory devices based on SAFs.

Design of magnetostrictive tactile sensor for depth detection

PurposeThis paper aims to design a magnetostrictive tactile sensor for surface depth detection. Unlike the human finger, although most tactile sensors have high sensitivity to pressure, they cannot detect millimeter-level depth information on the surface of objects precisely. To enhance the ability to detect surface depth information, a piezomagnetic sensor combining inverse magnetostrictive effect and bionic structure is developed in this paper.Design/methodology/approachA magnetostrictive tactile sensor based on Galfenol [(Fe83Ga17)99.4B0.6] is designed and studied for surface depth measurement. The optimal structure of the sensor is determined by experiment and theory. The test platforms for static and dynamic characteristics are set up. The static and the dynamic sensing performance of the sensor are studied experimentally.FindingsThe sensor can detect 0–2 mm depth change with a sensitivity of 91.5 mV/mm. A resolution of 50 µm can be achieved in the depth direction. In 50 cycles of loading and unloading tests, the maximum error of the sensor output voltage amplitude is only 2.23%.Originality/valueThe sensor can measure the depth information of object surface precisely with good repeatability through sliding motion and provide reference for object surface topography detection.

Enhanced magnetic modulation at a border of magnetic ordering in La1−xSrxMnO3/BaTiO3(100) heterostructure

In La1−xSrxMnO3 (LSMO)/BaTiO3 (BTO) heterostructures with a multiferroic interface, an artificial modulation of the magnetic structure is observed. The saturation magnetization of La1−xSrxMnO3 changes discontinuously due to in-plane distortions caused by a structural phase transition of a BaTiO3 substrate. Polarity reversal of the external electric field also causes a reversible switching in the magnetization. The magnitude of both magnetic modulations, due to the magnetoelastic and electric field effects, is concomitantly enhanced at a critical composition xc∼0.55, locating at a border of the magnetic phase transition. The polarity-dependent change in magnetization is possibly attributed to a change in the concentration of oxygen ions at the LSMO/BTO interface, indicating that the exchange interaction is reciprocally driven from being ferromagnetic to antiferromagnetic by the electric field polarity.

Quantification of electronic and magnetoelastic mechanisms of first-order magnetic phase transitions from first principles: application to caloric effects in La(FeSi)13

and derived quaternary compounds are well-known for their giant, tunable, magneto- and barocaloric responses around a first-order paramagnetic-ferromagnetic transition near room temperature with low hysteresis. Remarkably, such a transition shows a large spontaneous volume change together with itinerant electron metamagnetic features. While magnetovolume effects are well-established mechanisms driving first-order transitions, purely electronic sources have a long, subtle history and remain poorly understood. Here we apply a disordered local moment picture to quantify electronic and magnetoelastic effects at finite temperature in from first-principles. We obtain results in very good agreement with experiment and demonstrate that the magnetoelastic coupling, rather than purely electronic mechanisms, drives the first-order character and causes at the same time a huge electronic entropy contribution to the caloric response.

Ab initio statistical mechanics of the Néel transition in hexagonal YMnO3 : Antiferromagnetic domain walls, vortices, and local magnetoelectric coupling

Hexagonal manganites with coexisting antiferromagnetism and ferroelectricity have driven numerous research activities uncovering their potential in novel electronic devices. An antiferromagnetic order lowers the translational symmetry of the lattice; the structure of domain walls spatially separating distinctly ordered antiferromagnetic and structural states is quite rich and needs to be understood fundamentally. Here, we construct a model Hamiltonian to capture the low energy physics of coupled spins and phonons in hexagonal multiferroic ${\mathrm{YMnO}}_{3}$ derived from first-principles density functional theory and determine its temperature dependent behavior using Monte Carlo simulations. We demonstrate a weakly first order or close to being second order N\'eel transition accompanied by a $giant$ magnetoelastic effect observed experimentally in ${\mathrm{YMnO}}_{3}$ and show how it originates from the coupling between the in-plane ordering of spins with symmetry of ${\mathrm{\ensuremath{\Gamma}}}_{3}$ irreducible representation and collective atomic displacements with symmetry of ${\mathrm{\ensuremath{\Gamma}}}_{1}$ irreducible representation. We reveal the intriguing magnetic structure with the symmetry of ${\mathrm{\ensuremath{\Gamma}}}_{1}$ irreducible representation at the ${180}^{\ensuremath{\circ}}$ antiferromagnetic domain wall and predict a linear magnetoelectric coupling which can be confirmed using the piezoresponse force microscopy. Finally, we show that a stable magnetic vortex forms along a line of intersection of six ${60}^{\ensuremath{\circ}}$ antiferromagnetic domain walls, with energy comparable to that of dislocations in metals.

Sound Generation by Metro Trains during Braking and Its Suppression Method

The causes of acoustic noise occurring during braking of electric vehicles, in particular, in the metro, were analyzed. The spectrum of such noise was measured, and it is shown that high-frequency discrete tones are excited by braking resistors, applied for electrodynamic braking of electric vehicles. Three proposed mechanisms of electromechanical interaction in a Fecral plate, which is a braking resistor element, were considered: the Ampère force and linear and nonlinear magnetostriction. It was shown that predominant odd harmonics indicate the presence of a significant piezomagnetic effect and the inverse effect of linear magnetostriction in the Fecral alloy. A phenomenological approach was used to calculate the piezomagnetic tensor elements for Fecral. Calculations by the finite element method showed that asymmetric cuts introduced into the plate may significantly decrease intensity of acoustic vibrations excited by the braking resistor.

60∘ and 120∘ domain walls in epitaxial BaTiO3 (111)/Co multiferroic heterostructures

We report on domain pattern transfer from a ferroelectric ${\mathrm{BaTiO}}_{3}$ substrate with a (111) orientation of the surface to an epitaxial Co film grown on a Pd buffer layer. Spatially modulated interfacial strain transfer from ferroelectric/ferroelastic domains and inverse magnetostriction in the ferromagnetic film induce stripe regions with a modulation of the in-plane uniaxial magnetic anisotropy direction. Using spin-polarized low-energy electron microscopy, we observe the formation of two distinct anisotropy configurations between stripe regions, leading to angles of ${60}^{\ensuremath{\circ}}$ or ${120}^{\ensuremath{\circ}}$ between the magnetizations of adjacent domains. Moreover, through application of a magnetic field parallel or perpendicular to these stripes, head-to-head or head-to-tail magnetization configurations are initialized. This results in four distinct magnetic domain-wall types associated with different energies and domain widths, which, in turn, affects whether domain pattern transfer can be achieved.

Effect of Acoustic Oscillations on Non-Equilibrium State of Magnetic Domain Structure in Cubic Ni2MnGa Single Crystal.

Magnetic hysteresis is a manifestation of non-equilibrium state of magnetic domain walls trapped in local energy minima. Using two types of experiments we show that, after application of a magnetic field to a ferromagnet, acoustic oscillations excited in the latter can "equilibrate" metastable magnetic domain structure by triggering the motion of domain walls into more stable configurations. Single crystals of archetypal Ni2MnGa magnetic shape memory alloy in the cubic phase were used in the experiments. The magnetomechanical absorption of ultrasound versus strain amplitude was studied after step-like changes of a polarizing magnetic field. One-time hysteresis was observed in strain amplitude dependences of magnetomechanical internal friction after step-like variations of a polarizing field. We distinguish two ingredients of the strain amplitude hysteresis that are found in the ranges of linear and non-linear internal friction and show qualitatively different behavior for increasing and decreasing applied polarizing fields. The uncovered effect is interpreted in terms of three canonical magnetomechanical internal friction terms (microeddy, macroeddy and hysteretic) and attributed to "triggering" by acoustic oscillations of the irreversible motion of domain walls trapped in the metastable states. To confirm the suggested interpretation we determine the coercive field of magnetization hysteresis through the measurements of the reversible Villari effect. We show that the width of the hysteresis loops decreases when acoustic oscillations in the non-linear range of domain wall motion are excited in the crystal. The observed "equilibration" of the magnetic domain structure by acoustic oscillations is attributed to the periodic stress anisotropy field induced by oscillatory mechanical stress.

Competition between exchange and magnetostatic energies in domain pattern transfer from BaTiO3 (111) to a Ni thin film

We use spin-polarized low-energy electron microscopy to investigate domain pattern transfer in a multiferroic heterostructure consisting of a (111)-oriented ${\mathrm{BaTiO}}_{3}$ substrate and an epitaxial Ni film. After in situ thick-film deposition and annealing through the ferroelectric phase transition, interfacial strain transfer from ferroelastic domains in the substrate and inverse magnetostriction in the magnetic thick film introduce a uniaxial in-plane magnetic anisotropy that rotates by ${60}^{\ensuremath{\circ}}$ between alternating stripe regions. We show that two types of magnetic domain wall can be initialized in principle. Combining experimental results with micromagnetic simulations, we show that a competition between the exchange and magnetostatic energies in these domain walls has a strong influence on the magnetic domain configuration.

Design and Evaluation of a Magnetoelastic Tensile Force Sensor

Abstract This paper introduces the basic theory behind magnetoelastic sensors which are based on the change of magnetic properties (permeability) due to mechanical stress (Villari effect). A well-known magnetoelastic sensor, the Pressductor, is described. A simulation model of a sensor is created, described, and evaluated by computing the static transfer characteristic of RMS secondary coil voltage change due to tensile stress. A real sensor is then manufactured from a polycrystalline transformer sheet and experimentally tested by using a tensile load created by water weight. The simulation and experiment show similar behavior but are not completely identical which is most likely since some material properties were taken from literature rather than from experimental measurements, like the magnetostriction coefficient and initial magnetic susceptibility.

Boost the voltage of a magnetoelastic generator via tuning the magnetic induction layer resistance

Using the giant magnetoelastic effect in the soft systems for ambient energy harvesting, namely, the magnetoelastic generator (MEG), is challenged by its relatively low voltage output. A conventional transformer could be employed to solve the problem by increasing the voltage at the expense of current; however, it holds a bulky and rigid configuration with considerable energy loss. Here, we developed the resistance-controllable magnetic induction (MI) layer with multi-walled carbon nanotubes (MWCNT) as an inner transformer to manipulate the electrical output of an MEG. With high electrical conductivity, flexibility, and mechanical strength, the resistance of the MWCNT-based MI layer can be designed by thickness, width, length, and turns of the coils, contributing to a power-transforming effect. As the resistances increased, the open-circuit voltage increased, while the short-circuit current showed a reversed trend. With a power density of 0.23 mV cm−2, the power-transforming MEG can charge a commercial capacitor at a rate of 0.63 mV s−1 with intrinsic waterproofness. This work introduces a compelling approach to boost the voltage output of the MEG via internally engineering the resistance of the MI layer.

Equivalent Circuit Models for Magnetoelastic Resonance Sensors With Various Surface Loadings

Sensors based on the magnetoelastic (ME) effect have been developed for various applications, such as food safety, immunoassays, and health monitoring. A major obstacle to the widespread adoption of ME sensors is the poor understanding of the electrical impedances that constitute the system and how these impedances are influenced by surface loadings. Here, we derive a lumped-element model to approximately predict the near-resonance electrical behavior of an ME sensor simultaneously loaded with a mass layer and a semi-infinite Newtonian liquid. For more extensive applicability, a hybrid model, combining a modified Butterworth–Van Dyke (mBVD) model and a transmission line model, is derived for the first time to predict the response of the ME sensor under various surface conditions, including rigid solids, fluids, viscoelastic media, or any combinations thereof. The theoretical models are experimentally verified for accuracy and used to quantitatively analyze the mass, viscosity, and modulus of loadings by extracting the electrical parameters. This modeling work is crucial for the development of ME sensors in various applications and for providing insights into the physical mechanisms of advanced devices.

A strain-controlled magnetostrictive pseudo spin valve

Electric-field control of magnetism via an inverse magnetostrictive effect is an alternative path toward improving energy-efficient storage and sensing devices based on a giant magnetoresistance effect. In this Letter, we report on lateral electric-field driven strain-mediated modulation of magnetotransport properties in a Co/Cu/Py pseudo spin valve grown on a ferroelectric 0.7Pb[Mg1/3Nb2/3)]O3–0.3PbTiO3 substrate. We show a decrease in the giant magnetoresistance ratio of the pseudo spin valve with the increase in the electric field, which is attributed to the deviation of the Co layer magnetization from the initial direction due to strain-induced magnetoelastic anisotropy contribution. Additionally, we demonstrate that strain-induced magnetic anisotropy effectively shifts the switching field of the magnetostrictive Co layer, while keeping the switching field of the nearly zero-magnetostrictive Py layer unaffected due to its negligible magnetostriction. We argue that magnetostrictively optimized magnetic films in properly engineered multilayered structures can offer a path to enhancing the selective magnetic switching in spintronic devices.

Atomic scale understanding the periodic modulation in ferroelastic alloy Ni-Mn-Ti

Ferroelastic alloys with modulated martensites have shown promising functionalities, such as giant elastocaloric and magnetoelastic effects, but understanding of the periodic modulation has prompted much controversy between atomic shuffling (or periodic distortion) and adaptive phase (or nano-twinning, assembly of blocks with fixed lattice parameters) concepts. The main difficulty lies in the capturing of atomic re-arrangement process during the fast-kinetics martensitic transformation. In this work, in-situ cooling TEM (transmission electron microscopy) and HR-TEM investigations were carried out on a Ni50Mn32Ti18 Heusler alloy to visualize the atomic re-arrangement process from B2 austenite to 6O (6-layer modulated orthorhombic) and further to 4O (4-layer modulated orthorhombic) martensites. The results showed that the whole transformation involves modulation period change, lattice parameter adjustment, and gradual formation and dissociation of {110}<11¯0>B2-type stacking faults (SFs). In particular, the 6O and 4O phases have distinct lattice parameters in the tetragonal blocks if following the adaptive phase concept. The successive B2 to 6O and 4O transformation can be explained by the changes in both distance and period of {110}<11¯0>B2 shuffling. The experimental observations support that atomic shuffling may account for the formation of modulated martensites, at least, in the present Ni-Mn-Ti system. Consequently, this study, by providing atomic-scale evidence, may deepen the understanding of modulated phase transformation mechanism in an important class of functional alloys.