Search

The nonlinear splitting of magnetoelastic resonance line in powerfully excited ferrite is investigated. It is shown that the amplitude of splited resonance has the same order of value that the amplitude of basis resonance and its frequency is determined by the upper boundary of nonlinear amplitude-frequency characteristic of magnetic system. It is found the threshold character of splitting additional resonance from general. It is determined the possibility of operation of splited elastic resonance frequency by changing of exited magnetic field value which has practical importance. [ABSTRACT FROM AUTHOR]

In this work, we present the results of a systematic experimental study of linear and parametric spin wave resonant excitation accompanied by spin currents (spin pumping) in a multifrequency composite bulk acoustic wave resonator with a ZnO-YIG-GGG-YIG/Pt structure. The features of magnetic dynamics excitation in YIG films due to magnetoelastic coupling with acoustic thickness modes of various polarizations are studied. Acoustic spin waves and spin pumping are detected by simultaneous frequency-field mapping of the inverse spin Hall effect voltage and the resonant frequencies of thickness extensional modes. In the parametric range of frequencies and fields, acoustic spin pumping induced by both shear and longitudinal polarization modes was observed. Linear acoustic spin waves are excited only by shear thickness extensional modes because longitudinal acoustic waves do not couple with the magnetic subsystem in linear regime. [ABSTRACT FROM AUTHOR]

Strong and long-range coupling of the magnetization dynamics of the two antiferromagnetic layers mediated by the phonons transferred through a nonmagnetic insulator has been investigated. The magnetization dynamics in one of the antiferromagnetic layers via a magnetoelastic interaction leads to the excitation of phonons and their pumping to the nonmagnetic layer. The transfer of phonons, which carry angular momentum, through a nonmagnetic insulator from one antiferromagnetic layer to another, leads to an interference pattern in the absorption spectrum, which represents the coupling of magnetization dynamics of two layers.

The hybrid high overtone bulk acoustic wave resonators (HBARs) consisting of a piezoelectric film transducers and gallium gadolinium garnet substrates with yttrium iron garnet films (YIG-GGG-YIG) are used for experimental excitation and detection of acoustically driven spin waves (ADSWs). Two types of HBAR transducers made of Al-ZnO-Al films (differed through the electrodes’ geometry) were deposited onto YIG-GGG-YIG trilayers with different YIG film thicknesses and doping levels and served for excitation of multimode HBAR at gigahertz frequencies. ADSWs were detected by measuring the shifts of resonant HBAR modes in a tangential external magnetic field when the conditions for magnetoelastic resonance (MER) were satisfied. It was shown that the design of the transducer with a continuous bottom electrode provides all acoustical excitation of spin waves (pure ADSWs), suppressing the additional inductive magnetic dynamics excitation due to the electrodes’ geometry. The theoretical study of the HBAR spectrum in a magnetic field showed that the resonance harmonics in the MER region can either almost continuously transfer from one to another, or decay and form an evident magnetoelastic gap. In this case, the shift of resonant frequencies can achieve several intermodal distances. The results obtained are important for applications of HBAR-based devices in spintronics and magnonics.

In this paper, we report the first theoretical results on the acoustic generation of spin accumulation in ferromagnet-semiconductor-ferromagnet trilayers. As a representative material system, we consider a Ni/GaAs/Ni trilayer coupled to a piezoelectric transducer, which injects a planar acoustic wave into the adjoining Ni film. By combining an analytical solution of the spin diffusion equation in the GaAs spacer with results of numerical simulations of the coupled elastic and magnetic dynamics in the Ni films, we quantify an oscillating inhomogeneous spin accumulation in GaAs. It is found that both dc and ac parts of the mean spin accumulation vary nonmonotonically with the spacer thickness t S , reaching maximal values at t S mostly close to 0.25 or 0.75 of the wavelength of the injected monochromatic acoustic wave. Remarkably, the transverse wave generates the spin accumulation much more efficiently than the longitudinal one. Our theoretical predictions provide guidelines for the development and optimization of energy-efficient acoustic spin injectors into semiconductors, which should have much lower power consumption than injectors driven by the microwave magnetic field. [ABSTRACT FROM AUTHOR]

The hybrid high overtone bulk acoustic wave resonators (HBARs) consisting of a piezoelectric film transducers and gallium gadolinium garnet substrates with yttrium iron garnet films (YIG-GGG-YIG) are used for experimental excitation and detection of acoustically driven spin waves (ADSWs). Two types of HBAR transducers made of Al-ZnO-Al films (differed through the electrodes' geometry) were deposited onto YIG-GGG-YIG trilayers with different YIG film thicknesses and doping levels and served for excitation of multimode HBAR at gigahertz frequencies. ADSWs were detected by measuring the shifts of resonant HBAR modes in a tangential external magnetic field when the conditions for magnetoelastic resonance (MER) were satisfied. It was shown that the design of the transducer with a continuous bottom electrode provides all acoustical excitation of spin waves (pure ADSWs), suppressing the additional inductive magnetic dynamics excitation due to the electrodes' geometry. The theoretical study of the HBAR spectrum in a magnetic field showed that the resonance harmonics in the MER region can either almost continuously transfer from one to another, or decay and form an evident magnetoelastic gap. In this case, the shift of resonant frequencies can achieve several intermodal distances. The results obtained are important for applications of HBAR-based devices in spintronics and magnonics. [ABSTRACT FROM AUTHOR]

Magnetic characteristics of iron borate, FeBO3, film on diamagnetic gallium borate substrate were determined from electron magnetic resonance studies in the microwave frequency range of 15–36 GHz and the temperature range of 4 K to room temperature. The temperature dependence of the Dzyaloshinskii–Moriya field in the film is in accordance with that previously determined for FeBO3 single crystals. In contrast, the isotropic energy gap in the film is several times larger than in the single crystal. This discrepancy has been related to deformations caused by the mismatch between the lattice parameters of the film and the substrate. [ABSTRACT FROM AUTHOR]

Multiferroic composites with a large magnetoelectric response are gaining attractive interests for the design of magnetoelectric (ME) functional devices. In this work, the particulate ME composites (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3–xBaFe12O19 (x=0, 0.1, 0.2, 0.3, 0.4 and 1) were prepared, and their structural, dielectric, magnetic, ferroelectric, piezoelectric properties and magnetoelectric coupling were systematically investigated. The composites consisted of only two chemically separated phases with well-bonded interface. Dielectric and impedance analyses indicated the co-contribution of grain and grain boundary to polarization. Well-saturated ferroelectric and magnetic hysteresis loops demonstrated multiferroic nature. ME response was investigated elaborately by employing magnetically induced polarization, together with measuring ME voltage coefficient and magnetodielectric value. Specifically, a large ME coefficient of 26.78 ​mV/cm·Oe was achieved for x=0.3, which is higher than that in single-phase BaFe12O19 and its coupled composites.

• Symmetry analysis of magnetoelastic energy of trigonal magnets is carried out. • Higher orders invariants in magnetoelastic energy of trigonal magnets are constructed. • The possibilities for interpreting the effects in trigonal magnets are expanded. In expansion of the thermodynamic potential for a trigonal easy-plane antiferromagnet such as iron borate, FeBO 3 , magnetoelastic invariants of a higher order in the components of the deformation tensor and the antiferromagnetic vector with respect to those traditionally used were taken into account. Such invariants make it possible to describe new effects observed in iron borate crystals and composites based on them. [ABSTRACT FROM AUTHOR]

Highlights • Hypersonic composite resonator with ZnO-GGG-YIG/Pt layered structure. • The self-consisted theory for acoustically driven spin waves and spin currents. • Acoustic spin pumping in magnetoelastic/piezoelectric layered structures. • Detection of acoustically driven spin waves by means of inverse spin Hall effect. • Optimal YIG film thickness for spin pumping in spintronic acoustical resonator. Abstract We report on the self-consisted semi-analytical theory of magnetoelastic excitation and electrical detection of spin waves and spin currents in hypersonic bulk acoustic waves resonator with ZnO-GGG-YIG/Pt layered structure. Electrical detection of acoustically driven spin waves occurs due to spin pumping from YIG to Pt and inverse spin Hall (ISHE) effect in Pt as well as due to electrical response of ZnO piezotransducer. The frequency-field dependences of the resonator frequencies and ISHE voltage U ISHE are correlated with experimental ones observed previously. Their fitting allows to determine some magnetic and magnetoelastic parameters of YIG. The analysis of the YIG film thickness influence on U ISHE gives the possibility to find the optimal thickness for maximal U ISHE value. [ABSTRACT FROM AUTHOR]

The combination of magnetostrictive thin films with surface acoustic wave (SAW) devices enables the magnetic sensors that exploit the ΔE-effect (magnetically induced change in modulus) without the need for free-standing structures that are susceptible to vibration and damage. The performance of these sensors is strongly influenced by magnetic anisotropy and, therefore, the state of stress in the magnetostrictive film. We report the fabrication and characterization of magnetic SAW devices comprised of a magnetostrictive layer and interdigital transducers on a piezoelectric substrate. The state of stress in the magnetostrictive layer is varied by annealing. Vibrating-sample magnetometer measurements indicate that the annealed devices show a strong uniaxial anisotropy with the easy axis parallel to the direction of acoustic propagation. The induced magnetic anisotropy is attributed to the anisotropic thermal expansion in the substrate. The change in frequency of one-port resonators and two-port SAW oscillators is measured as a function of dc bias field and ambient temperature. The normalized change in frequency (Δf/fsat) is on the order of 10-4. These results demonstrate that the film stress can be used to optimize the performance of magnetic SAW devices and the SAW devices can be used to characterize the state of stress and magnetic anisotropy of magnetostrictive films. [ABSTRACT FROM AUTHOR]

This work presents the results of experimental and theoretical studies of the magnetic properties of the LiYb F 4 single crystal and powder samples, and magnetoelastic properties of the LiYb F 4 single crystal samples, at low temperature and applied field range of 0-9 T. The magnetostriction experimental data for the single crystal of LiYb F 4 is published for the first time. The magnetization and magnetostriction were calculated in the framework of the exchange-charge model taking into account dipole–dipole and electron-deformation interactions, with the calculation of the electron-deformation parameters. The theoretical analysis presents quantitative agreement in the temperature range of 2–10 K with the magnetization and magnetostriction measurements of the LiYb F 4 samples. • Experimental magnetostriction data shows high anisotropy of the magnetoelastic properties. • Exchange-charge model describes magnetic properties of LiYb F 4 crystals at 2 < T < 300 K. • Magnetic properties of LiYb F 4 single crystal have four-fold symmetry. • Set of electron-deformation parameters for LiYb F 4 was calculated. [ABSTRACT FROM AUTHOR]

Raman spectra of Ho1−xNdxFe(BO3)4 (x=1, 0.75, 0.5, 0.25) have been studied in temperature range 10–400K. Two compositions (x=1, x=0.75) demonstrate structural phase transition with soft mode restoration. The addition of Nd atoms increases interatomic spacing and decreases the temperature of structural phase transition. The solid solutions (x=0.75, 0.5, 0.25) demonstrate the emergence of the peaks corresponding to magnetoelastic interaction below Néel temperature. The order parameter of the magnetic phase transition has been determined. The equal concentrations of holmium and neodymium atoms prevent magnon soft modes condensation caused by exchange interactions in Fe–O–Fe chains are observed. Calculations confirm the data obtained in the experiment.

The latest experimental advances have extended the scenario of coupling mechanical degrees of freedom in chiral magnets (MnSi/MnGe) to the topologically nontrivial skyrmion crystal and even monopole lattices. Equipped with a spin-wave theory highlighting the topological features, we devise an interacting model for acoustic phonons and magnons to explain the experimental findings in a monopole lattice with a topological phase transition, i.e. annihilation of monopole–antimonopole pairs. We reproduce the anisotropic magnetoelastic modulations of elastic moduli: drastic ultrasonic softening around the phase transition and a multi-peak-and-trench fine structure for sound waves parallel and orthogonal to the magnetic field, respectively. Comparison with experiments indicates that the magnetoelastic coupling induced by Dzyaloshinskii–Moriya interaction is comparable to that induced by the exchange interaction. Other possibilities such as elastic hardening are also predicted. The study implies that the monopole defects and their motion in MnGe play a crucial role.

• Consistent approach to the interpretation of thermal expansion in magnetic crystals is developed. • FeBO 3 – a trigonal antiferromagnet with weak ferromagnetism – is used as a model object. • Different character of the thermal expansion above and below the magnetic ordering temperature is described taking into account magnetostrictive deformations. • A model based on the symmetry of the crystal and its domain structure is put forward. • The temperature dependences of magnetoelastic constants over a wide temperature range and the hitherto unknown constants are determined. Iron borate FeBO 3 – a trigonal antiferromagnet with weak ferromagnetism – was used as a model object for experimental and theoretical studies of thermal expansion. X-ray diffraction analysis indicated that the character of the thermal expansion changes significantly when passing through the Néel point. In the magnetically ordered state below the phase transition temperature, the thermal changes in the crystal lattice parameters are additionally affected by magnetostrictive deformations. A theoretical model was developed that allows interpreting experimental data and determining the magnetoelastic constants using X-ray diffraction analysis. Temperature dependences of some of the magnetoelastic constants of iron borate were determined, and the hitherto unknown constants were found. These data are essential to describe various phenomena associated with magnetoelastic interactions in magnetically ordered materials. [ABSTRACT FROM AUTHOR]

The heating temperature effect on field dependences of the Δ E-effect of amorphous wires of FeSiB treated by direct current with the simultaneous application of tensile stresses are investigated. Concepts of the effect of the magnetoelastic interaction of the core and the near-surface regions of wires on temperature variations of field dependences of the Δ E-effect are developed. [ABSTRACT FROM AUTHOR]

The influence of temperature on the dependences of the Δ E effect of FeSiB metallic amorphous wires, which were subjected to thermomagnetic treatment at temperatures of from 370 to 470°C, on the magnetic field has been studied. It was shown that, at all temperatures of thermomagnetic treatment at relatively low heating temperatures, the negative Δ E effect is observed. The increase in the heating temperature of the wire during measurements of the Δ E effect at temperatures of 30-330°C leads to a decrease in both the magnitude of negative Δ E effect and the field of reaching the maximum Δ E effect magnitude. The dependence of the induced anisotropy field on the heating temperature of the wire has been determined. The obtained results are explained based on the concept of magnetoeleastic interactions between the core of wire and its near-surface area. [ABSTRACT FROM AUTHOR]

Abstract: The phase transitions on the material constants in a semi-infinite ferromagnet with mechanic boundary conditions and competing “inclined” ease-axis anisotropy and easy-plane anisotropy have been investigated. The phase states and the spectra of coupled magnetoelastic waves have been researched. The analysis of the spectra of elementary excitations allowed the construction of the phase diagram of the system. [Copyright &y& Elsevier]

The magnetic characteristics of a film under the effect of an external indenter have been studied. It has been shown that magnetoelastic interactions induce additional magnetic anisotropy, which can be either positive or negative, depending on the values of the magnetoelastic constants. The effect of the geometrical parameters of the problem on the magnetoelastic energy has been investigated. [ABSTRACT FROM AUTHOR]

Abstract: In the present article two effects, which were observed previously in the ferromagnetic shape memory alloys, are explained using the concept of internal pressure influencing the crystal lattice. The first effect is the noticeable change of the temperature dependence of Young''s modulus at the Curie point and the second one is the quasi-second-order martensitic transformation of the alloy. It has been shown that the larger the volume change, which accompanies the martensitic transformation of the alloy, the more pronounced the influence of internal pressure on the second- and third-order elastic modulus of the alloy. If the volume change is larger than or equal to 0.5%, the magnetoelastic pressure in the Ni–Mn–Ga alloy is large enough to induce the experimentally observed change of the temperature dependence of Young''s modulus at the Curie point. The internal pressure created by the structural defects of the alloy has been considered. It has been shown that in the case where the internal pressure destabilizes the martensitic phase, the martensitic transformation becomes similar to a second-order phase transition. [Copyright &y& Elsevier]

Abstract: An ion-pair compound 1,6-bis(1-methylimidazolium)hexane bis(maleonitrio-dithiolato)nickelate was synthesized and structurally characterized. This compound crystallizes in the triclinic space group P-1, and the anions form the alternating stacks in the crystal. Reversible three-step solid-to-solid phase transitions occur at ~210, ~320 and ~432K upon cooling. The entropy change of phase transition was estimated to be 25.4J⋅K−1⋅mol−1 and 9.97J⋅K−1⋅mol−1 for the transitions at ~320 and ~432K, respectively. The hysteresis effect was observed in the χm–T plot for the transitions at ~210 and ~320K. The mechanisms of transitions are discussed based on the crystal structure and thermal analyses. [Copyright &y& Elsevier]

Abstract: The phase states of the 2D non-Heisenberg ferromagnetic with anisotropic bilinear and biquadratic exchange interactions are investigated. The limiting cases of the system under consideration are the two-dimensional XY-model with biquadratic exchange interaction and the isotropic Heisenberg ferromagnetic. The account of the magnetic dipole interaction leads to the realization of spatially inhomogeneous quadrupolar phase. The stability regions of various phase transitions for different values of the material parameters are studied. The phase diagram is built. Besides, the temperature phase transitions are investigated. The influence of the magnetoelastic interaction on the formation of the long-range quadrupolar order is determined. [Copyright &y& Elsevier]

Abstract: Direct parametrical amplification of ultrasound was theoretically considered for the ferromagnetic/piezoelectric thin-layered structure composites, for which within the long-wavelength approach some, material specific, yet homogeneous bulk properties could be assumed. Having chosen appropriate homogeneous components, it is possible to construct a desirable composite with such properties that are absent in the starting-up “building blocks” (components). Sound frequencies are assumed to be such that only the dispersion due to magnetic subsystem is thought relevant; the piezoelectric components are set to have a nonlinear dielectric response. Presence of orientational phase transition for the ferromagnetic subsystem allows to vary frequency of a ferromagnetic resonance, and consequently to alter the dispersion at the chosen frequency of sound. While solving coupled equations describing dynamics of mechanical, magnetic and piezoelectric subsystems, an effective sound amplification for realistic values of physical parameters is shown possible. [Copyright &y& Elsevier]

Abstract: Concentration-driven reorientation phase transitions in ultrathin magnetic films of FeCo alloy have been studied. It is established that, in addition to the easy-axis and easy-plane phases, a spatially inhomogeneous phase (domain structure), a canted phase, and also an “in-plane easy-axis” phase can exist in the system. The realization of the last phase is associated with the competition between the single-ion anisotropy and the magnetoelastic interaction. The critical values of Co concentration corresponding to the phase transitions are evaluated, the types of phase transitions are determined, and the phase diagrams are constructed. [Copyright &y& Elsevier]

Based on the magnetoelastic generalized variational principle and Hamilton’s principle, a dynamic theoretical model characterizing the magnetoelastic interaction of a soft ferromagnetic medium in an applied magnetic field is developed in this paper. From the variational manipulation of magnetic scale potential and elastic displacement, all the fundamental equations for the magnetic field and mechanical deformation, as well as the magnetic body force and magnetic traction for describing magnetoelastic interaction are derived. The theoretical model is applied to a ferromagnetic rod vibrating in an applied magnetic field using a perturbation technique and the Galerkin method. The results show that the magnetic field will change the natural frequencies of the ferromagnetic rod by causing a decrease with the bending motion along the applied magnetic field where the magnetoelastic buckling will take place, and by causing an increase when the bending motion of the rod is perpendicular to the field. The prediction by the mode presented in this paper qualitatively agrees with the natural frequency changes of the ferromagnetic rod observed in the experiment. [ABSTRACT FROM AUTHOR]

Abstract: The dynamic stability of a soft ferromagnetic rectangular and simply supported plate immersed in an applied transverse magnetic field, as well as subjected to an in-plane periodic compression is presented in this paper. The fundamental equations involving magnetoelastic interaction and magnetic damping effect for the ferromagnetic plate are developed. In the theoretical model, the expression of induced magnetic force is based on a generalized magnetoelastic variational model, and the magnetic damping is due to the Lorentz body force arising from eddy current in the ferromagnetic material. By means of a linearized magnetoelastic theory and perturbation technique, the motion equation of the ferromagnetic plate is reduced to a damped Mathieu''s equation and solved. The dynamic stability of the magnetoelastic system without in-plane compression is theoretically analyzed first, to show that there exist two stable states: magnetic damped stable oscillation, and over-damped asymptotically stable motion before static divergence instability of the ferromagnetic plate occurs. The dynamic instability and stability regions for the parametric excitation of the ferromagnetic plate due to the harmonically excited in-plane compression are obtained next. The effects of magnetic damping and excitation frequency of the in-plane periodic compression on the stability regions are discussed in detail. [Copyright &y& Elsevier]

Abstract: The giant magnetoimpedance is the sensitive change in ac impedance value with the application of dc magnetic field when ac current passes through the sample. In the present work GMI properties of positive (Fe77.5Si7.5B15), negative (Co72.5Si12.5B15) and nearly zero ((Co94Fe6)72.5Si12.5B15) magnetostrictive amorphous wires have been studied. The result indicates that the magnetostriction constant plays an important role in GMI property. The maximum GMI ratio (330%) and maximum field sensitivity (7% per A/m) are observed in (Co94Fe6)72.5Si12.5B15 amorphous wire. The frequency response of the GMI characteristics of the above alloys has been measured and zero magnetostrictive (Co94Fe6)72.5Si12.5B15 material showed better frequency response. [Copyright &y& Elsevier]

In this paper we propose a method to calculate the torsional deformations induced in film–substrate systems by magnetostrictive strains. The calculation scheme proposed assumes that the magnetostriction phenomenon can be modeled in terms of anisotropic expansional strains. These strains are incorporated into the classical plate theory to formulate an energy minimization problem, which is solved using a Ritz method. To illustrate the method we use a cantilever plate in which the film and the substrate are mechanically isotropic and a saturating magnetic field is applied in a direction parallel to the plane of the plate. Our calculations show that the deformation induced by an in-plane field generally includes twisting as well as bending deflection. The cases in which only one of these deflections is present are discussed. One of the advantages of the method proposed is that it can be used regardless of the relative thickness of the substrate with respect to that of the film. It also allows us to consider cases in which a film–substrate system deforms due to piezoelectric, thermal or hygroscopic expansional strains. [Copyright &y& Elsevier]

With the aid of a generalized variational method, in this paper, a theoretical model for soft ferromagnetic shells is derived to describe their magnetoelastic behavior in an applied magnetic field. Having made a quantitative comparison between the numerical predictions given by several theoretical models and the experimental results on strains of a cylindrical shell, we find that the predictions got by our model are in good agreement with the experimental data. It is also found that the Moon’s model is a special case of the model derived in this paper when the relative magnetic permeability μr>104, which confirms that it is reasonable for the Moon’s model to calculate strains of the soft ferromagnetic shells. Having displayed the distribution of the equivalent magnetic force in the length of the cylindrical shell and its circumferential bending strains with different elastic end constraints, we give an explanation for the discrepancy between Moon’s analytical results and his experimental ones. [Copyright &y& Elsevier]

Influence of magnetoelastic (ME) interaction on the phase transitions in two-dimensional non-Heisenberg ferromagnets is investigated. It is shown that if the constant of Heisenberg exchange interaction is large, the ferromagnetic phase is implemented in a system. When the value of biquadratic exchange interaction increases there is a phase transition to the quadrupolar phase characterized by the tensor order parameters. Thus, ME interaction plays an essential role, not only stabilizing the long-range magnetic order in the system, but also determining the order of the phase transition. [Copyright &y& Elsevier]

The magnetoelastic interaction effect on the process of the 90° pulses switching in iron borate monocrystals is investigated. A simple comparing of the magnetization switching rate and the intensity of the magnetoelastic oscillations following the switching process shows that the break on the switching curve is accounted for by the sharp decreasing of the energy loss connected with the magnetoelastic oscillations. In its turn these decreasing of the energy loss is due to the lag of the elastic subsystem of the crystal from the magnetic one at the switching time τ&les;τ*&ap;15±2 ns. The value of τ* is practically independent on both the monocrystal thickness and the reversal process mode. [Copyright &y& Elsevier]

In this paper the generation of harmonic waves in an elastic magneticmaterial, which is a perfect conductor of electricity, isconsidered. It has been assumed that an infinite body is subjected tothe action of an initially constant magnetic fieldH = (H,0,0) and in the plane ax+by=0 acts a source ofdistortion. It has been shown that this source may produce bothtransverse and longitudinal waves and each of them consists of two parts,which propagate with different speeds. The amplitudes and speeds in dependence on theangle between the direction of wave propagation and the magnetic fieldintensity H have been discussed. [ABSTRACT FROM AUTHOR]