Intrinsic Magnetostriction Research Articles

Ultrasensitive magnetostrictive responses at the pre-transitional rhombohedral side of ferromagnetic morphotropic phase boundary

The morphotropic phase boundary (MPB) has been utilized extensively in ferroelectrics and recently been extended to ferromagnets, especially for the magnetostrictive materials. Here, guided by phenomenological theories and phase-field simulations, we proposed a design strategy for obtaining the ultrasensitive magnetoelastic response at the pre-transitional rhombohedral side of ferromagnetic MPB, by further flattening the energy landscape while maintaining large intrinsic magnetostriction. To validate this, we judiciously introduced the light-rare-earth-based $$\hbox {Tb}_{0.1}\hbox {Pr}_{0.9}$$ system to the Co-doped $$\hbox {Tb}_{0.27}\hbox {Dy}_{0.73}\hbox {Fe}_{2}$$ alloy, as $$\hbox {Tb}_{0.1}\hbox {Pr}_{0.9}$$ is an anisotropy compensation system with large intrinsic strains and the transition metal dopant of Co tends to optimize the magnetostriction. Phase-field modeling was used to determine the detailed magnetic domain evolution of the investigated multi-component Laves phase compounds, the results of which were compared with experimental results. At room temperature, an ultrahigh magnetoelastic response $${d}_{33}$$ was found in $$\hbox {Tb}_{0.253}\hbox {Dy}_{0.657}\hbox {Pr}_{0.09}(\hbox {Fe}_{0.9}\hbox {Co}_{0.1})_{2}$$ recompensation system especially at low fields, which is superior to that of the commercial $$\hbox {Tb}_{0.27}\hbox {Dy}_{0.73}\hbox {Fe}_{2}$$ (Terfenol-D) polycrystal. The ultrahigh magnetostrictive sensitivity, together with low raw material cost makes it one of the strongest candidates for magnetostriction applications.

Sign-changed-magnetostriction effect of morphotropic phase boundary in pseudobinary DyCo2−DyFe2 Laves compounds

The morphotropic phase boundary (MPB) has recently attracted considerable interest in a number of pseudobinary $R{T}_{2}$ (R is rare earth; T is a 3d-transition metal) Laves phase compounds for achieving enhanced large magnetostriction or near zero magnetostriction. Unlike the MPBs separating a tetragonal and a rhombohedral phase in the literature, here we report that in the $\mathrm{DyC}{\mathrm{o}}_{2}\text{\ensuremath{-}}\mathrm{DyF}{\mathrm{e}}_{2}$ system, the ferromagnetic MPB separating two tetragonal phases of different tetragonality can also lead to a sign-changed-magnetostriction effect. Synchrotron x-ray diffraction data demonstrate the coexistence of two tetragonal phases in the broadening MPB regime, one with $c/al1$ (T1 phase) and the other with $c/ag1$ (T2 phase). The preferable domain switches of the T1 phase with weaker magnetocrystalline anisotropy under low fields and the subsequent domain switches of the T2 phase with stronger magnetocrystalline anisotropy under high fields give rise to the sign-changed-magnetostriction effect. Further analysis suggests that the MPB effect on the magnetostrictive response is determined by the intrinsic magnetostriction, the magnetocrystalline anisotropy, as well as the magnetic ordering of two end terminals that form the MPB. This work reveals another type of MPB in pseudobinary $R{T}_{2}$ compounds and provides an effective recipe for designing sign-tunable magnetostrictive materials.

Effects of intrinsic magnetostriction on tube-topology magnetoelectric sensors with high magnetic field sensitivity

Three quasi-one-dimensional magnetoelectric (ME) magnetic field sensors, each with a different magnetostrictive wire material, were investigated in terms of sensitivity and noise floor. Magnetostrictive Galfenol, iron-cobalt-vanadium, and iron-nickel wires were examined. Sensitivity profiles, hysteresis effects, and noise floor measurements for both optimally biased and zero-biased conditions are presented. The FeNi wire (FN) exhibits high sensitivity (5.36 mV/Oe) at bias fields below 22 Oe and an optimal bias of 10 Oe, whereas FeGa wire (FG) exhibits higher sensitivity (6.89 mW/Oe) at bias fields >22 Oe. The sensor of FeCoV wire (FC) presents relatively low sensitivity (2.12 mV/Oe), due to low magnetostrictive coefficient. Each ME tube-topology sensor demonstrates relatively high sensitivity at zero bias field, which results from a magnetic shape anisotropy and internal strain of the thin magnetostrictive wire.

Giant low-temperature magnetostriction and spin-reorientation of polycrystalline alloy PrFe1.9

A remarkably giant intrinsic magnetostriction λ111 as high as 6700 ppm was found at 70 K in PrFe1.9 compound, which is much larger than the value of 5600 ppm predicted by single-ion theory. Change of the easy magnetization direction from [111] to [100] with decreasing temperature occurs between 30 and 70 K, which was verified by step-scanned {440} and {222} X-ray diffraction reflections. It was further demonstrated that this compound has a rhombohedral symmetry between 70 and 300 K, and a tetragonal symmetry between 15 and 30 K. Therefore, the magnetostrictive anomaly at low temperature may be interpreted by the spin reorientation transition of the compound. PrFe1.9 with high magnetostriction is a good candidate material for magnetostriction applications at low temperature.

Tb-Dy-Fe-Co合金本征磁致伸缩性能

λ 100. Tb0.3Dy0.7Fe1.95 ,C o λ111 , λ100 , λ s . ABSTRACT The distribution of Co, the intrinsic magnetism and magnetostriction of quater- nary Tb-Dy-Fe-Co alloy were investigated. The SEM image showed the matrix (Laves phase) and the rare-earth (RE) rich phase in the annealed samples. The Co content (atomic fraction) in the RE rich phase was 21.18%, much higher than that in the matrix (9.36%). XRD pat- terns showed that Co partial substitution for Fe did not change the structure of MgCu2-type cu- bic Laves phase, contributing to the giant magnetostriction. Curie temperature Tc was increased remarkably with Co addition, resulting in wider operating temperature. The magnetocrystalline anisotropy compensation by Co addition was beneficial to improving the magnetostriction in low field. The solidified orientation influences the testing of intrinsic magnetostriction. In order to en- sure the accuracy in the measurements, the equiaxed Tb-Dy-Fe-Co samples were prepared. The saturated magnetostrictive constant λs was tested. λ111 and λ100 were calculated by the cleav- age of (440) diffraction peak of Laves phase. Compared with Terfenol-D alloy, λ111 in the Co- doped sample decreased slightly, but λ100 increased evidently and λs almost remained unchanged.

Measurement of Intrinsic Magnetostriction in Fe–Ga Alloys

The recent development of differential X-ray absorption spectroscopy (DiffXAS) has presented a unique opportunity to bridge the gap that presently exists between macroscopic experimental measurements of magnetostriction, and theoretical models that naturally describe behaviour at an atomic level. Such measurements are capable of explicitly probing the strain between individual pairs of atoms, and thus can be said to measure a sample's intrinsic magnetostriction. This paper will elaborate on the technical aspects of recent DiffXAS measurements from the important Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">81</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">19</sub> alloy; providing a full description of the DiffXAS technique, its features and requirements, and study the process of extracting atomic-scale strain information from the resulting spectra.

Magnetostriction of Ce xTb 1− xFe 2 compounds

In this paper, the magnetostriction of Ce x Tb 1− x Fe 2 compounds was investigated using a standard strain gauge technique, and the intrinsic magnetostriction of Ce x Tb 1− x Fe 2 compounds was derived from fitting the (4 4 0) peak of the X-ray diffraction pattern. It is found that the magnetostriction of Ce x Tb 1− x Fe 2 compounds decreases slowly with increasing Ce content at low Ce content, while decreases sharply at high Ce content. X-ray diffraction analysis shows that the intrinsic magnetostriction decreases with the Ce concentration increasing in Ce x Tb 1− x Fe 2 compounds, and the Ce ion contributes to the magnetostriction.

Inductive write heads using high-moment pole materials for ultrahigh-density demonstrations

In this paper, the high moment materials and their applications in the write heads for these areal density demonstrations will be discussed. Due to high intrinsic magnetic anisotropy and magnetostriction, which is typically about 4.5x10/sup 5/, FeCoN films exhibit typical coercivity in excess of 50 Oe, and isotropic in-plane magnetic properties, under un-optimised process conditions. A typical hysteresis loop of the film is shown.

The potentiality of composite elastic magnets as novel materials for sensors and actuators

Abstract In the last decade the progress of standard magneto-elastic materials is going toward its physical limits. New horizons are recently opened by the development of artificial composites having both elastic and magnetic properties. The working principle of these elastomagnetic materials is not depending on intrinsic magnetostriction, but on the coupling between magnetic moments of the particles and particles themselves. The possibility to study the physical mechanism that relates the elastic and magnetic properties in the new scenery furnished by composites of magnetic particles in an elastic matrix is very promising from the basic knowledge point of view. On the other side, the potential competitiveness in several applications justifies the increasing efforts to improve the production and to perform technical characterization of these magnetoelastic composites in different experimental conditions.

Structure and Electrical Properties of Gold Nanowires Grown with Electrochemical Deposition

The effect of Al substitution for Fe on the structure, magnetostriction, anisotropy and spin reorientation of a series Of Tb-0.3 Dy-0.7 (Fe1-xAlx)(1.95) alloys (x = 0, 0.05, 0.1, 0.15, 0.20, 0.25, 0.30, 0.35) at room temperature has been investigated. It was found that all the compositions of Tb-0.3 Dy-0.7 (Fe1-xAlx)(1.95) substantially retained the MgCu2-type C-15 cubic Laves phase structure and the lattice constant increases with increasing x. The substitution of Al increases slightly the magnetostriction in low magnetic field ( H less than or equal to 40kA.m(-1)) when x 0.15. The intrinsic magnetostriction lambda(111) decreases sharply also with incresasing x. The Mossbauer spectra show that for 0 less than or equal to x 0.15. The measurements of relative susceptibility indicate that the temperature of spin reorientation decreases with increasing x.

Structural, magnetic, Mössbauer and magnetostrictive studies of amorphousTb(Fe0.55Co0.45)1.5films

Films with a nominal composition of Tb(Fe0.55Co0.45)1.5 werefabricated by rf-magnetron sputtering from a fixed target configuration atvarious Ar gas pressures. Samples were investigated by means of x-raydiffraction (XRD), scanning electron microscopy (SEM), vibrating samplemagnetometer (VSM), conversion electron Mössbauer spectra (CEMS) andmagnetostriction measurements. As the Ar pressure increases, the Tb and Fecontent increases slightly, whereas the Co content decreases. In addition, asmall amount of Ar is introduced into the films. The as-deposited films areamorphous alloys, but their magnetic behaviour depends strongly on thedeposition conditions: a perpendicular magnetic anisotropy is obtained only infilm deposited at lowest Ar pressure and a parallel magnetic anisotropyexhibits in remaining films. These samples show an intrinsic magnetostriction(λ≈10-3) in an applied field of 0.7 T. In this state, it wasdetermined that the hyperfine field reaches the value Bhf = 24.5 T. Effectsof the heat treatment on the magnetostrictive softness are also reported. Theparallel magnetostriction with a huge magnetostrictive susceptibility(χλ = 1.8×10-2 T-1) obtained at (µ0H = 10 mT)makes these materials useful for applications.

Magnetic, Mössbauer and magnetostrictive studies of amorphous Tb(Fe0.55Co0.45)1.5 films

The Tb(Fe0.55Co0.45)1.5 films were fabricated by rf magnetron sputtering from a composite target. Samples were investigated by means of x-ray diffraction, vibrating sample magnetometer, conversion electron Mössbauer spectra, and magnetostriction measurements. The as-deposited film is an amorphous alloy with a perpendicular magnetic anisotropy and an intrinsic magnetostriction λ=1080×10−6 in an applied field of 0.7 T. In this state, it was determined that the hyperfine field Bhf=23.5 T and the cone-angle between the Fe moment direction and the film-normal direction β=12°. After annealing in the temperature range of TA=250–450 °C the amorphous structure still remained, however the anisotropy was changed to a parallel one. The soft magnetostrictive behavior has also been improved by these heat treatments: the parallel magnetostriction λ∥=465×10−6 was almost developed in low applied fields of less than 0.1 T and, especially, a huge magnetostrictive susceptibility χλ=dλ∥/d(μ0H)=1.8×10−2 T−1 was obtained at μ0H=15 mT.

Formation of induced anisotropy in amorphous Sm–Fe based thin films by field sputtering

Induced anisotropy with a large energy of 6×104 J/m3 is formed in an amorphous Sm–Fe based thin film by sputtering under an applied magnetic field of 500–600 Oe. The induced anisotropy results in a large anisotropy in magnetostriction, a strain anisotropy ratio reaching as high as 35, although intrinsic magnetostriction is affected only slightly. The large strain anisotropy allows one to realize a large strain in a particular direction and, hence, it is of significant practical importance. Induced anisotropy is also found to be formed by postannealing under applied magnetic field, but the magnitude of anisotropy energy formed is very small.

Giant magnetostrictive effects in magnetic oxides

Experimental research on giant magnetostrictive effects in magnetic oxides is reviewed. Particular attention is paid to manganates, cobaltates, high-temperature superconductors and spin-Peierls material CuGeO 3. The magnetostrictive effects are analysed in terms of recently developed theoretical models. It is shown that strong electron–phonon coupling is responsible for intrinsic giant magnetostriction in most of the oxides presented. In the case of high-temperature superconductors the giant forced magnetostriction is due to extrinsic effects related to flux-pinning and consequently to lattice defects.

Magnetostriction of TbyDy1-y(Fe1-xTx)2(T=Al,Mn) and Their Intrinsic Magnetostrictive Properties

Magnetostriction of TbyDy1-x(Fe1-xTx)2(T=Al,Mn) single crystals, prepared by the MCGS-3 CZ instrument, was investigated. The intrinsic magnetostrictive properties were derived by fitting method of X-ray diffraction patterns of polycrystal samples prepared by arc-melting method. The substitution of AL, Mn for Fe lowers the saturation field and magnetocrystalline anisotropic energy. The intrinsic magnetostriction, 111, decreases with increasing amount of Al or Mn. For Tb0.5Dy0.5(Fe0.9Mn0.1)2 single crystals,a large magnetostriction and high d33 can be obtained under the compressive stress of 1226 MPa.

FMR and SMFMR study of Fe/Si multilayers

In this paper the investigations of magnetic and magnetoelastic properties of Fe/Si multilayers are presented. The multilayers have been grown by dc sputtering on the single - crystal GaAs substrates. Ferromagnetic resonance (FMR) measurements were performed at the frequency of 9.4 GHz and in the temperature range from liquid helium to room temperature before and after illumination with 514nm light. The magnetostriction constant of investigated films has been measured at room temperature by strain modulated ferromagnetic resonance (SMFMR) method. An attention is given to the effect of the interface on the observed effective saturation magnetostriction. The FMR and SMFMR measurements mostly revealed the contribution from interface to the observed spectra. The results were analyzed taking into account both the alloying effects and the intrinsic surface anisotropy and magnetostriction. It was shown that in the case of Fe/Si multilayers the effect of alloying prevails.

Stress dependence of magnetostrictions and strains in 〈111〉-oriented single crystals of Terfenol-D

Single crystals of Tb0.27Dy0.73Fe2 were prepared successfully by the Czochralski (CZ) method using a magnetic levitation cold crucible first in this laboratory. The Laue x-ray technique and metallography verified its twin-free single crystalline perfection. Weidmanstatten precipitation (WSP) slightly exists in these specimens with WSP platelets parallel to the {111} planes of Terfenol-D. Saturation magnetostriction were measured along three principal crystallographic axes [111], [11 2̄] and [1 1̄0] of single crystal Tb0.27Dy0.73Fe2 with magnetic field parallel and then perpendicular to the measuring direction, which gives an intrinsic magnetostriction λ111=1640×10−6 for 〈111〉 easy axis. Stress dependence of magnetostrictions and strains measured along three mutually perpendicular axes, [111], [11 2̄], and, [1 1̄0] on 〈111〉-oriented single crystalline rods of Terfenol-D indicates that apparent magnetostriction for 〈111〉 direction increases with increasing applied compressive stress along the rod axis, and reaches 2375×10−6 under a stress of 24 MPa and a magnetic field of 20 kOe. Maximum d33 decreases with the increment of applied stresses and the amount of WSP, and ranges from 1×10−6/Oe to 6×10−6/Oe at about 500 Oe. Less hysteresis appears. Magnetizing processes are calculated and compared with the measured changes of magnetostriction. The authors conclude that 〈111〉-oriented single crystal of Terfenol-D is suitable for precise displacement actuators although it would be much better to eliminate the WSP precipitation.

Magnetostriction of Fe/Gd multilayers

Using strain-modulated ferromagnetic resonance method we have measured the magnetostriction constant λ s of Fe/Gd multilayers deposited using rf and dc sputtering. For the samples deposited using rf sputtering the contribution to the effective magnetostriction due to the interdiffusion layers has been observed. Samples grown using dc sputtering are characterized by sharp interfaces with no indication of interdiffusion. In his case the magnetostriction consists of two components: one due to the bulk magnetostriction and another due to the intrinsic surface magnetostriction.

Elastic and magnetoelastic behaviour of nanoscale magnetic multilayers

Experimental and theoretical research on elastic and magneto-elastic behavior of nanoscale magnetic multilayers is reviewed. The discovery of the supermodulus effect and the softening of the elastic constants as well as the experimental evidence for the existence of the intrinsic are discussed in detail. It has been shown that the commonly observed lattice expansion perpendicular to the film plane is not a bulk effect, but is localized at the interface between the contacting metals. A similar situation is observed in the ease of magnetoelastic strains. It is shown that the most effective technique used to study magnetostriction is the Strain Modulated Ferromagnetic Resonance (SMFMR). In addition to obtaining information on the magnetostriction constants, the SMFMR method offers the opportunity to study the interface effects, particularly it can be used to separate the intrinsic surface magnetostriction from the interface induced effects. The origin of the surface magnetostriction will be discussed and qualitatively attributed to many different mechanisms. Quantitatively the surface magnetostriction will be analyzed in terms of magnetic dipole-dipole interactions. >

Magnetoelastic effects in sputtered Ni/Ti multilayers

Magnetoelastic tensor components M/sub 11/ and M/sub 12/ for Ni/Ti multilayers are measured at room temperature using strain modulated ferromagnetic resonance (SMFMR). The dependence of M/sub 11/ and M/sub 12/ on the inverse Ni layer thickness is interpreted as mainly due to anisotropic volume and isotropic interface interactions. It is suggested that the SMFMR method provides the possibility of distinguishing between intrinsic surface magnetostriction and interdiffusion effects. >