Magnetoelastic Properties Research Articles

Structural, magnetic and magnetoelastic properties of Laves-phase Tb0.3Dy0.6Nd0.1(Fe1-xCox)1.93 compounds (0 ≤ x ≤ 0.40)

Structure, magnetization and magnetostriction of Tb0.3Dy0.6Nd0.1(Fe1-xCox)1.93 (0 ≤ x ≤ 0.40) compounds have been investigated. X-ray diffraction (XRD) analysis shows the presence of single Laves phase with a cubic MgCu2-type structure. The easy magnetization direction (EMD) is observed to be <111> direction when x ≤ 0.10, and deviates away with further increasing Co contents. The Co contributes an opposite role in the resultant magnetocrystalline-anisotropy compared to Tb. A small amount of Co substitution for Fe can enhance the Curie temperature for x ≤ 0.25. The magnetocrystalline-anisotropy compensation can be achieved in this system. A minimum in anisotropy is obtained for the Tb0.3Dy0.6Nd0.1(Fe0.8Co0.2)1.93 compound, which has good magneto-elastic properties, e.g., the large saturation magnetostriction λS (∼930 ppm) and the high low-field magnetostriction λa (∼670 ppm/3 kOe), and may make it technological interest in the field of magnetostrictive materials.

Magnetoelastic properties of Co-doped Laves compounds TbxHo0.9−xNd0.1Fe1.93 (0≤x≤0.40)

Structure, spin configuration, magnetocrystalline-anisotropy compensation, magnetization, and magnetostriction of TbxHo0.9-xNd0.1(Fe0.8Co0.2)(1.93) (0 axis when x >= 0.25, accompanied by a rhombohedral distortion with large spontaneous magnetostriction coefficients lambda(111). The anisotropy compensation can be achieved by evaluating EMD, magnetization and magnetostriction, and the critical point is realized to be around x = 0.25. The good magnetoelastic properties, e.g., the low anisotropy at room temperature, high polycrystalline saturation magnetostriction (lambda(s) similar to 560 ppm) and large spontaneous magnetostriction coefficient (lambda(111) similar to 850 ppm), are achieved for the Tb0.25Ho0.65Nd0.1 (Fe0.8Co0.2)(1.93) compound, which may make it a promising magnetostrictive material. (C) 2015 Elsevier Ltd. All rights reserved.

Influence of Zr doping on the structural, magnetic and magnetoelastic properties of cobalt-ferrites

Cobalt-ferrite (CoFe2O4) has long been identified as a potential material for the magnetostrictive component of the torque sensor − for power-steering systems in automotive industries, owing to its superior strain sensitivity (dλ/dH). In this work we investigate the influence of Zr doping (in Fe site) on the structural, magnetic, and magnetoelastic properties of CoFe2O4. Zr-doped cobalt-ferrites, having nominal compositions Co1+xZrxFe2−2xO4 (0⩽x⩽0.2), were synthesized by conventional solid-state method. The X-ray spectral analysis indicated the presence of only cubic-spinel phase and the lattice parameter (a) increases from ∼8.3769Å (x=0) to ∼8.3921Å (x=0.2). Saturation magnetization (MS), at ∼4000kA/m, and coercivity (HC) increases from ∼413kA/m and ∼4.456kA/m respectively for x=0 to ∼540kA/m, ∼7.96kA/m respectively for x=0.2. A remarkable 300% increase in dλ/dH was observed in Zr-doped cobalt-ferrite sample (x=0.2) (∼3.32×10−9A−1m) compared to that of pure cobalt-ferrite (∼0.8×10−9A−1m).

Anomalies in magnetoelastic properties of DyFe11.2Nb0.8 compound

The structural and magnetic properties of DyFe11.2Nb0.8 compound have been investigated by high intensity, high resolution synchrotron x-ray diffraction, ac magnetic susceptibility, and dc magnetization measurements as well as Mössbauer spectroscopy (5–300 K). The easy magnetization direction at room temperature is along the c-axis. With decreasing temperature, the magnetocrystalline anisotropy changes from easy-axis to easy-cone at Tsr2 (∼202 K), then to easy plane at Tsr1 (∼94 K). The thermal expansion coefficient obtained from the synchrotron x-ray study exhibits clear anomalies around both of the spin reorientation transition temperatures. The 57Fe hyperfine interaction parameters and magnetic moments values have been determined for the 8i, 8j, and 8f sites from the Mössbauer spectra.

Anisotropy study of multiferroicity in the pyroxene NaFeGe2O6

We present a study of the anisotropy of the dielectric, magnetic and magnetoelastic properties of the multiferroic clinopyroxene NaFeGe2O6. Pyroelectric currents, dielectric constants and magnetic susceptibilities as well as the thermal expansion and the magnetostriction were examined on large synthetic single crystals of NaFeGe2O6. The spontaneous electric polarization detected below in an antiferromagnetically ordered state () is mainly lying within the ac plane with a small component along , indicating a triclinic symmetry of the multiferroic phase of NaFeGe2O6. The electric polarization can be strongly modified by applying magnetic fields along different directions. We derive detailed magnetic field versus temperature phase diagrams and identify three multiferroic low-temperature phases, which are separated by a non-ferroelectric, antiferromagnetically ordered state from the paramagnetic high-temperature phase.

Investigation of Magnetic and Magnetoelastic Properties of the Unconventional Heavy-fermion Compound CeCu2Ge2

Heavy-fermion compounds, high-Tc cuprates or iron pnictides are characterized by adjacent properties and a rich magnetic phase diagram with unconventional or competing states at low temperatures. CeCu2Ge2, the counterpart of the heavy-fermion superconductor CeCu2Si2, exhibits an incommensurate antiferromagnetically long-range ordered ground state with τ1 = (0.28 0.28 0.54) up to TN = 4.1K which is strongly affected by a screening of the Ce 4f-moments by conduction electrons expressed by a Kondo temperature of TK = (6–10) K.The similar energy scales of the magnetic exchange and the Kondo effect result in a complex magnetic phase diagram with the possibility of quantum criticality at very low temperatures. The magnetic properties of CeCu2Ge2 were studied by magnetization measurements and, using the strong magnetoelastic coupling, by magnetostrictive investigations over a wide temperature range and in fields up to 50 T. Especially, the magnetostriction curves reveal clearly the details of the temperature and field dependence of the phase transitions. Here we present experimental results used for a refinement of the H − T phase diagram in [100] and [110] direction.

Investigation of the Interaction of Magnetic Field With the Auxetic Behavior of Galfenol

Iron-Gallium alloy (Galfenol) is a magnetostrictive material (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sat</sub> ~ 400 ppm) with potential for robust transduction. In addition, Galfenol is auxetic in the <;110> direction with Poisson's ratio values of as low as -0.7. In recent years, this phenomenon has been examined with several experimental protocols. The negative Poisson's ratio of Fe-Ga (attributed to lattice softening under applied stresses) has been documented using tensile tests (with and without a dc magnetic bias) and resonant ultrasound spectroscopy. In addition, density functional theory has been used to produce simulations that explain atomic mechanisms for the observed highly auxetic behavior in this alloy. This paper examines the auxetic response of Galfenol to varying magnetic fields and zero applied stress. An energy based mathematical model of the coupled magnetoelastic properties of the alloy is derived and used to predict Poisson's ratio at magnetic saturation. The results from this approach with no mechanical excitation shows an increase in the Poisson's ratio with increase in the Ga content of the alloy. This is opposite to the trends observed with applied stresses where there is a decrease in the Poisson's ratio with increase in the Ga content. Experimental results for Galfenol of compositions between 15 and 33 atomic percent Gallium will be presented and compared with values from the magnetoelastic model.

Comparison of magnetoelastic properties between the 〈110〉 oriented TbxDy1-xFe1.95 polycrystalline alloys with different Tb/Dy composition ratio under magnetomechanical loading

This paper presents comparison of magnetoelastic properties between the 〈110〉 oriented Tb x Dy 1-x Fe 1.95 polycrystalline alloys for x = 0.27, 0.3, 0.45 under coupled loading of magnetic field and compressive stress. The simultaneously measure are investigated for the magnetization and magnetostriction under applied magnetic field from -200 to 200 kA/m and compressive stress from 0 to 50 MPa along the rod axis at room temperature. The results show that, according to the increase of Tb concentration and compressive stress, the hysteresis, coercive force and magnetostriction hysteresis loops of Tb x Dy 1-x Fe 1.95 alloys increase rapidly and the distortion of the hysteresis loops occurs at higher compressive stress, especially Tb 0.45 Dy 0.55 Fe 1.95 alloys, while the maximum relative permeability of Tb x Dy 1-x Fe 1.95 alloys monotonously decrease. Meanwhile, the higher the Tb concentration the stronger is magnetostrictive "jump" effect. For these experimental results, the effect of compressive stress and Tb / Dy ratio on magnetoelastic properties of Tb x Dy 1-x Fe 1.95 alloys are coupling and remarkable. A tradeoff and optimization are very important for many engineering designs and applications.

Magnetoelastic Clock System for Nanomagnet Logic

In recent years, magnetic-based technologies, like nanomagnet logic (NML), are gaining increasing interest as possible substitutes of CMOS transistors. The possibility to mix logic and memory in the same device, coupled with a potential low power consumption, opens up completely new ways of developing circuits. The major issue of this technology is the necessity to use an external magnetic field as clock signal to drive the information through the circuit. The power losses due to the magnetic field generation potentially wipe out any advantages of NML. To solve this problem, new clock mechanisms were developed, based on spin transfer torque current and on voltage-controlled multiferroic structures that use magnetoelastic properties of magnetic materials, i.e., exploiting the possibility of influencing magnetization dynamics by means of the elastic tensor. In particular, the latter shows an extremely low power consumption. In this paper, we propose an innovative voltage-controlled magnetoelastic clock system aware of the technological constraints risen by modern fabrication processes. We show how circuits can be fabricated taking into account technological limitations, and we evaluate the performance of the proposed system. Results show that the proposed solution promises remarkable improvements over other NML approaches, even though state-of-the-art ideal multiferroic logic has in theory better performance. Moreover, since the proposed approach is technology-friendly, it gives a substantial contribution toward the fabrication of a full magnetic circuit and represents an optimal tradeoff between performance and feasibility.

Magnetoelastic Properties of Selected Amorphous Systems Tailored by Thermomagnetic Treatment

Abstract Magnetoelastic properties of Fe6iCoigSÍ5Bi5 alloy after thermomagnetic treatment were tested for both compressive and tensile stresses, what is significant novelty. Results of presented investigation opens new ways of modelling the magnetoelastic effects in amorphous systems tailored by thermomagnetic treatment.

Magnetodeformation and elastic properties of ferrogels and ferroelastomers

The work deals with a theoretical study of magnetoelastic properties of soft composite materials, consisting of a polymer matrix filled with micron-sized magnetizable particles (ferrogels and ferroelastomers). The systems with a homogeneous gas-like spatial distribution of particles in the matrix are considered. The impact of the particles magnetic interaction on the macroscopic elastic characteristics of the composites is studied. Analysis shows that this interaction increases elastic moduli of the materials. This effect must be especially significant for the composites with soft gel matrix.

Effect of non-magnetic ion substitution on the magnetoelastic properties of CoFe2O4 films

We report on the structural and magnetic properties of CoFe1.9Zr0.1O4 films under epitaxial strain. The films are grown with high structural quality on MgO, SrTiO3, and piezoelectric Pb(Mg1∕3Nb2∕3)0.72Ti0.28O3 substrates by pulsed laser deposition. The substrate-induced strain is found effective to alter the magnetic anisotropy of the films. Reversible strain measurements using the piezoelectric substrates are providing evidence that nearly bulk-like magnetoelastic properties are maintained for films of down to at least 25 nm thickness. This is in contrast to unsubstituted cobalt ferrite films and suggests that a chemical control of the spinel lattice provides a promising route to optimize the tunability of the magnetic properties of thin ferrite films.

Electro-mechanical character of Gd and Gd2In and possibility of a Kondo-like behavior in Gd2In

The elastic constants of Gd-element and Gd2In have been determined by density functional theory (DFT). Mechanical properties have been specified and compared with available experimental results. In this work, a detailed ab initio study on Gd and Gd2In are presented in order to investigate the magneto-elastic and electronic properties and to consider the tune parameters involved in these values. The relationship between these data and the possibility of Kondo-like effect in Gd2In were discussed.

Features of Magnetic, Magnetoelectric and Magnetoelastic Properties of HoAl&lt;sub&gt;3&lt;/sub&gt;(BO&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;4&lt;/sub&gt;

The main features of the magnetic, magnetoelastic and record magnetoelectric properties of a HoAl3(BO3)4 alumoborate single crystal have been studied experimentally and theoretically. ForB||awe have observed a giant polarization ΔPba(Ba) ≈ –5240 µС/m2 induced by field of 9 T at T = 5 K. We have calculated the magnetic characteristics of HoAl3(BO3)4 in the framework of a crystal-field model. The parameters of the crystal-field in HoAl3(BO3)4 have been determined. Good agreement of experimental and calculational magnetization curves Mc,^с(В) and the temperature dependences of magnetization Mс,^с(T) was achieved. For interpretation of magnetostriction in HoAl3(BO3)4 the field and temperature dependences of the multipole moments have been calculated.

Influence of Tensile Stress on the Surface Magneto-Optical Hysteresis Loops in Amorphous and (Nano)Crystalline Ribbons

The behavior of the surface magnetic anisotropy in the amorphous and (nano)crystalline ribbons is investigated using the magneto-optical (MO) methods. In this paper, the differential intensity MO method is extended by the specially designed sample holder suitable for applying the tensile stress in the ribbon axis. Measured surface hysteresis loops, represented as a function of tensile stress <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">$\sigma$ </tex-math></inline-formula> , offer an interesting insight into the magnetoelastic properties of the ribbon surface phases. These dependencies are studied and discussed in the case of the surface-crystallized <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">${\rm Co}_{66}{\rm Fe}_{4}{\rm Si}_{15}{\rm B}_{15}$ </tex-math></inline-formula> and the as-quenched amorphous <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">${\rm Fe}_{77.5}{\rm Si}_{7.5}{\rm B}_{15}$ </tex-math></inline-formula> ribbons. It is shown that the response of the surface crystalline phases and the amorphous matrix on applied stress is significantly different. This is manifested by the changes in the value and sign of magnetostriction coefficient <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">$\lambda_{s}$ </tex-math></inline-formula> . Good agreement between the surface and bulk magnetostriction is obtained for the FeSiB ribbons that are amorphous in the volume as well as on the surface.

Magnetoelastic properties of substituted Er1−xGdxMn6Sn6 intermetallic system

The forced magnetostriction of polycrystalline samples of Er1−xGdxMn6Sn6 (0≤x≤1) intermetallics with hexagonal HfFe6Ge6-type structure is investigated in the temperature range of 77–480K. Gd substitution has a significant effect on interatomic distances and especially on inter-sublattice R–Mn couplings. The replacement of Er by Gd results in increasing the ordering temperature followed by reinforcement of the R–Mn coupling, as well as decreasing the magnetostriction values owing to the S-state character of Gd3+ ions. The results show that the contribution of Er sublattice to anisotropic magnetoelastic effects is positive, while that of Gd and Mn is negative. All the examined samples exhibit considerable magnetovolume anomalies at the ordering temperature (TC=338, 381, 412 and 434K for the samples with x=0, 0.2, 0.6 and 1.0, respectively). While the unsubstituted sample exhibits metamagnetic transitions, Gd-contained compounds do not show this behavior, owing to the strong Gd–Mn coupling. The experimental results obtained are discussed in the framework of the two-magnetic sublattice by bearing in mind the lattice parameter dependence of the interlayer Mn–Mn exchange interaction in these layered compounds. From the temperature dependence of magnetostriction values and considering the magnetostriction equation for a hexagonal structure, we attempt to determine the signs of some of the magnetostriction constants for these compounds and the influence of Gd substitution on them.

Enhanced magnetoelectric effects in composite of piezoelectric ceramics, rare-earth iron alloys, and shape-optimized nanocrystalline alloys

An enhancement for magnetoelectric (ME) effects is studied in a three-phase ME architecture consisting of two magnetostrictive Terfenol-D (Tb(0.3)Dy(0.7)Fe(1.92)) plates, a piezoelectric PZT (Pb(Zr,Ti)O3) plate, and a pair of shape-optimized FeCuNbSiB nanocrystalline alloys. By modifying the conventional shape of the magnetic flux concentrator, the shape-optimized flux concentrator has an improved effective permeability (μ(eff)) due to the shape-induced demagnetizing effect at its end surface. The flux concentrator concentrates and amplifies the external magnetic flux into Terfenol-D plate by means of changing its internal flux concentrating manner. Consequently, more flux lines can be uniformly concentrated into Terfenol-D plates. The effective piezomagnetic coefficients (d(33m)) of Terfenol-D plate and the ME voltage coefficients (α(ME)) can be further improved under a lower magnetic bias field. The dynamic magneto-elastic properties and the effective magnetic induction of Terfenol-D are taken into account to derive the enhanced effective ME voltage coefficients (α(ME,eff)), the consistency of experimental results and theoretical analyses verifies this enhancement. The experimental results demonstrate that the maximum d(33m) in our proposed architecture achieves 22.48 nm/A under a bias of 114 Oe. The maximum α(ME) in the bias magnetic range 0-900 Oe reaches 84.73 mV/Oe under the low frequency of 1 kHz, and 2.996 V/Oe under the resonance frequency of 102.3 kHz, respectively. It exhibits a 1.43 times larger piezomagnetic coefficient and a 1.87 times higher ME voltage coefficient under a smaller magnetic bias of 82 Oe than those of a conventional Terfenol-D/PZT/Terfenol-D composite. These shape-induced magnetoelectric behaviors provide the possibility of using this ME architecture in ultra-sensitive magnetic sensors.

Kerr microscopy studies of the effects of bending stress on galfenol

This work deals with using a magneto-optic Kerr effect (MOKE) microscope to optically analyze the evolution of magnetic domains in a rolled and Goss textured galfenol (Fe81Ga19 + 1.0% NbC) sample when subjected to a bending stress. The initial magnetization state of the cantilevered sample was fixed along its length by a 0.3 T permanent magnet. The magnetic state was monitored with the MOKE microscope as a tip load was applied to bend the sample. The magnetic state of galfenol depends on its magneto-elastic properties. A finite element model that incorporates an energy based formulation of magnetostriction [W. D. Armstrong, J. Magn. Magn. Mater. 263(1–2), 208–218 (2003)] was used to investigate the stresses in the sample and the corresponding change in the magnetic induction as bending occurred. A qualitative comparison with the domain pictures is presented, and the experimental micromagnetic behavior results are shown to correlate well to the macro scale bending stress and magnetization results obtained in the FEM simulations.

Magneto-thermal conduction and phonon anomalies across magnetic transitions in multiferroic (poly and nanocrystalline) bismuth ferrite

Bismuth ferric oxide (BFO) or bismuth ferrite is a multiferroic material with perovskite structure in which ferroelectric and antiferromagnetic orderings coexist. The magneto-electric coupling in this material makes it interesting from fundamental physics and applications points of view. As a result of complex magneto-elastic coupling and spin-glass behavior at low temperatures, the material exhibits a number of phase transitions driven by magnetic ordering. Earlier reports indicate that the primary order parameter in these transitions is not polarization but are related to magnon mode softening. In order to throw more light on the magneto-elastic and phonon related properties of this material, we measured the thermal transport properties, thermal conductivity and specific heat capacity, in the presence of an external magnetic field and compared the results with the zero field case. Results are reported for polycrystalline as well as nanocrystalline samples of BFO between 140K and 250K. A photopyroelectric thermal wave technique has been employed for the measurements. Anomalies in thermal properties observed at 140K, 200K and 240K in polycrystalline samples as well as their changes with applied field are explained in terms of magneto-elastic and spin–phonon couplings. It is found that the transitions get less well defined and one of the transition temperatures get shifted upwards considerably as the particle sizes are reduced to nanometer scales. Particle size dependences of phonon and magnon–phonon scattering are invoked to explain these results.

Magnetic and magnetoelastic properties of LiDyF4 single crystals

Temperature and magnetic field dependences of the magnetization of LiDyF4 single crystal were measured with a dc-SQUID magnetometer. The longitudinal magnetostriction was measured by the capacitance-bridge method. A giant compression of the crystal lattice up to 0.1% was observed in the magnetic field of 1 T along the [110] direction at 4.2 K. Experimental data are well reproduced by simulations based on the microscopic models of the single-ion magnetoelastic and inter-ion multipole interactions.