Magnetoelastic Properties Research Articles

Infrared magnetoreflection in CoFe2O4 single crystals

Magnetoreflection of unpolarized infrared radiation for single crystals of magnetostrictive cobalt ferrite spinel was studied. The correlation between magnetoreflection and magnetoelastic properties of that type of spinel was observed. It is shown that the magnetoreflection is the most pronounced in the region of a middle-infrared impurity band and reflection minima near phonon bands.

Magnetoelastic properties of epoxy resin based TbxHo0.9−xNd0.1 (Fe0.8Co0.2)1.93 particulate composites

Abstract TbxHo0.9−xNd0.1 (Fe0.8Co0.2)1.93 (0 ⩽ x ⩽ 0.40) particulate composites were prepared by embedding and aligning alloy particles in an epoxy matrix with and without a magnetic curing field. The magnetoelastic properties were investigated as functions of composition, particle volume fraction and macroscopic structure of the composite. The magnetic anisotropy compensation point was found to be around x = 0.25, where the easy magnetization direction (EMD) at room temperature was detected lying along ⟨ 1 1 1 ⟩ axis. The composite with ⟨ 1 1 1 ⟩ preferred orientation and pseudo-1-3 type structure was prepared under an applied magnetic field of 12 kOe. An enhanced magnetoelastic effect and large low-field magnetostriction λa, as high as 430 ppm at 3 kOe, were obtained for Tb0.25Ho0.65Nd0.1 (Fe0.8Co0.2)1.93 composite rod. The value of λa was of 72 % of its polycrystalline alloy (~595 ppm/3 kOe) although it only contained 30 vol.% of the alloy particles. This enhanced effect can be attributed to the larger λ111 (as compared to λ100), low magnetic anisotropy, easy magnetization direction (EMD) along the ⟨ 1 1 1 ⟩ axis and ⟨ 1 1 1 ⟩-textured orientation of the alloy particles as well as the chain-like structure of the composite. The good magnetoelastic properties of the composite, in spite of the fact that it contained only 30 vol.% of the alloy particles with light rare-earth Nd element in the insulating epoxy, would make it a potential material for magnetostriction application.

Ferrogels based on entrapped metallic iron nanoparticles in a polyacrylamide network: extended Derjaguin-Landau-Verwey-Overbeek consideration, interfacial interactions and magnetodeformation.

A new kind of ferrogel with entrapped metallic iron nanoparticles causing unusual magnetodeformation is presented. Crosslinked polyacrylamide (PAAm) based ferrogels embedded with iron nanoparticles (MNPs) were synthesized by free radical polymerization in aqueous medium. Spherical iron MNPs with average diameter 66 nm were synthesized by the electrical explosion of wire and modified by interfacial adsorption of linear polyacrylamide (LPAAm). Extended Derjaguin-Landau-Verwey-Overbeek (xDLVO) calculations based on the superposing of van der Waals, electrostatic, steric, and magnetic contributions showed that polymeric encapsulation of nanoparticles by LPAAm is one of the most suitable pathways for preparing stable aqueous dispersions of iron nanoparticles. Microcalorimetry confirmed the presence of strong interfacial adhesion forces between LPAAm chains and the surface of iron nanoparticles. By keeping the same crosslinking density of a polymer network (i.e. 100 : 1, monomer to crosslinker ratio) and varying the initial monomer concentration, an influence of the extent of polymer network reticulation on the mechanical properties and subsequently, magneto-elastic properties was demonstrated. It was found that the upper limit of the shear modulus for the synthesis of a new kind of polyacrylamide based ferrogel to exhibit any usable magnetodeformation under the application of a uniform external magnetic field of 420 mT is ca. 1 kPa. Magnetodeformation of cylindrical ferrogel samples was observed in the form of an overall volume contraction accompanied by a homogeneous decrease in all dimensions. The deformation was found to be maximum (around 10%) for the aspect ratio of 1/1 and it was lower and similar for the samples with 1/2 and 2/1 aspect ratios. Such a type of magnetic response is significantly different from the behavior observed in the existing reports on ferroelastomers.

Dilatometric study of the metamagnetic and ferromagnetic phases in the triple-layered Sr4Ru3O10 system

The Ruddlesden Popper series Sr${}_{n+1}$Ru${}_{n}$O${}_{3+n+1}$ contains highly interesting physical phenomena depending on the number of RuO${}_{2}$ layers in the unit cell, spanning from unconventional superconductivity for the $n$=1 member Sr${}_{2}$RuO${}_{4}$ to itinerant ferromagnetism in the infinite-layer system SrRuO${}_{3}$. Obviously, the unique interplay between electronic, spin, and lattice degrees of freedom in this group of correlated itinerant electron systems leads to a tremendous change of the physical properties. This is also demonstrated by anisotropic and orbital-dependent magnetism and a strong spin-phonon coupling found in many members within the series. This paper focusses on triple-layer Sr${}_{4}$Ru${}_{3}$O${}_{10}$, which becomes ferromagnetic at ${T}_{c}$$\ensuremath{\sim}$105 K and shows a metamagnetic transition below ${T}^{*}$$\ensuremath{\sim}$50 K for a magnetic field along the $a\phantom{\rule{0}{0ex}}b$ plane. The authors investigate the magnetoelastic properties of this compound as a function of temperature and magnetic field. The high-resolution thermal expansion and magnetostriction measurements indicate a highly anisotropic response with a specific rearrangement of the crystal lattice in fields parallel and perpendicular to the $c$ axis. Finally, they reconstruct the $T$-$H$ phase diagram, which shows a new feature suggestive of the multiple-orbital character of Sr${}_{4}$Ru${}_{3}$O${}_{10}$, where both the ferromagnetic (${d}_{x\phantom{\rule{0}{0ex}}y}$) and the metamagnetic orbitals (${d}_{x\phantom{\rule{0}{0ex}}z;y\phantom{\rule{0}{0ex}}z}$) coexist and interact.

Reflection and transmission of SH-waves at a corrugated interface between two semi-infinite anisotropic magnetoelastic half-spaces

An analysis has been carried out for reflection and transmission of a plane SH-wave incident at a corrugated interface between two anisotropic magnetoelastic half-spaces. Rayleigh’s method of approximation is applied to derive the reflection and transmission coefficients for first order approximation of corrugation. The expressions for reflection and transmission coefficients for first order approximation of corrugation are obtained in closed form for a special type of interface. It is found that these coefficients are proportional to the amplitude of corrugation and are functions of magnetoelastic properties of materials of the half-spaces as well as the angle of incidence. Special cases are deduced for anisotropic and isotropic materials for particular case of corrugation. Numerical computations are performed for a specific model of two different anisotropic magnetoelastic media. The effects of anisotropic magnetoelastic coupling parameter, the angle at which wave crosses the magnetic field, frequency factor, wave length of corrugation, and the amplitude of corrugation are shown through figures.

Anomalous magnetoelastic behaviour near morphotropic phase boundary in ferromagnetic Tb1-xNdxCo2 system

In this work, we report a morphotropic phase boundary (MPB) involved ferromagnetic system Tb1-xNdxCo2 and reveal the corresponding structural and magnetoelastic properties of this system. With high resolution synchrotron X-ray diffractometry, the crystal structure of the TbCo2-rich side is detected to be rhombohedral and that of NdCo2-rich side is tetragonal below their respective Curie temperatures TC. The MPB composition Tb0.35Nd0.65Co2 corresponds to the coexistence of the rhombohedral phase (R-phase) and tetragonal phase (T-phase). Contrary to previously reported MPB involved ferromagnetic systems, the MPB composition of Tb0.35Nd0.65Co2 shows minimum magnetization which can be understood as compensation of sublattice moments between the R-phase and the T-phase. Furthermore, magnetostriction of Tb1-xNdxCo2 decreases with increasing Nd concentration until x = 0.8 and then increases in the negative direction with further increasing Nd concentration; the optimum point for magnetoelastic properties lies towards the rhombohedral phase. Our work not only shows an anomalous type of ferromagnetic MPB but also provides an effective way to design functional materials.

ChemInform Abstract: Magnetic and Magnetoelastic Properties of Valence Transition Compounds Based on YbInCu4 (Review Article)

AbstractReview: 78 refs.

Magnetoelastic auxetic‐like behavior in Galfenol: Experimental data and simulations

Iron–gallium alloy (galfenol) is a body centered cubic (BCC) magnetostrictive alloy that, like many other BCC metals, is auxetic in the ⟨110⟩{100} directions. For compositions of 12–33 at.% gallium, Poisson ratio (ν) values as low as −0.7 are observed along these directions in response to a uniaxial elastic force (tensile tests, resonant ultrasound spectroscopy, etc.). In 2014, Raghunath and Flatau first reported that galfenol also exhibits positive strain in both these directions when the uniaxial force applied along the ⟨110⟩{100} directions is provided solely by a magnetic field, i.e., with no external mechanical/elastic force or stress being applied to the alloy [Raghunath and Flatau, IEEE Trans. Magn. 50(11), 1–4 (2014)]. The observed response is a result of the intrinsic, atomic‐scale, bi‐directionally coupled magnetoelastic properties of these alloys. In this paper, we advance the understanding of the intrinsic atomic‐scale magnetoelastic coupling of the alloy that leads to the observed magnetoelastic auxetic‐like behavior by presenting simulations developed based on density functional theory, which we show match the experimental findings and energy‐based simulations. The elastic anisotropy and the electronic mechanisms that lead to magnetoelastic auxetic‐like behavior in galfenol are discussed.

Enhanced magnetoelastic effect in Laves (Tb,Dy)Fe2 alloys with the joint introduction of Pr and Nd

The structural and magnetoelastic properties of (Tb0.3Dy0.7)1−x(Pr0.5Nd0.5)xFe1.93 (0 ≤ x ≤ 0.20) polycrystalline alloys have been investigated by means of X-ray diffraction (XRD), a vibrating sample magnetometer and a standard strain gauge technique. A single (Tb,Dy,Pr,Nd)Fe2 Laves phase with a cubic MgCu2-type structure is formed when x ≤ 0.12, while a small amount of impurities appear when x ≥ 0.15. The easy magnetization direction at room temperature is detected toward axis. The analysis of XRD, magnetization and magnetostriction shows that the Pr and Nd elements joint introduction into (Tb,Dy)Fe2 system can reduce the magnetocrystalline anisotropy and improve the magnetoelastic properties. The (Tb0.3Dy0.7)0.88(Pr0.5Nd0.5)0.12Fe1.93 alloy exhibits a high low-field magnetostriction λa (~314 ppm/1 kOe), a large spontaneous magnetostriction coefficient λ111 (~1710 ppm), a giant saturation magnetostriction λS (~1060 ppm) and the low magnetocrystalline anisotropy at room temperature, and may make it a promising candidate for magnetostriction applications.

Spectroscopic investigation of elastic and magnetoelastic properties of CoFeB thin films

Magneto-stress coupling has been studied in Co20Fe60B20 thin films of varying thicknesses (10, 20 and 250 nm) deposited onto flexible substrate. It has been investigated by measuring the magnetic resonance under uniaxial (tensile or compressive) applied stresses in situ. The benchmark state, in terms of elastic and magnetic properties, was studied by combining Brillouin light scattering experiments and magnetic resonance experiments on flat samples. The deduced parameters are thickness-independent and close to the ones obtained using rigid substrates. A large uniaxial anisotropy proportional to the applied uniaxial stress is found, which is well fitted by considering an isotropic saturation magnetostriction coefficient. Finally, the angular dependence of the resonance field with in-plane biaxial stresses is probed and explained using a simple analytical model.

Magnetostriction of Laves Tb0.1Ho0.9−xPrx(Fe0.8Co0.2)1.93 alloys

Alloys of Tb0.1Ho0.9−xPrx(Fe0.8Co0.2)1.93 (0≤x≤0.50) are arc melted and investigated for structural, magnetic and magnetoelastic properties. The alloys possess predominantly the cubic Laves phase with MgCu2-type structure for x≤0.20, while impurities are observed for x≥0.30. The easy magnetization direction (EMD) rotates from <100> to <111> axis when x increases from 0 to 0.50, demonstrating the magnetocrystalline-anisotropy compensation between Pr3+ and Ho3+ ions. The linear anisotropic magnetostriction λa=(=λ∥−λ⊥) increases with increasing Pr content when x≤0.30, ascribed to both the larger magnetostriction of PrFe2 than that of HoFe2 and the decrease of the resulted anisotropy due to compensation. The Tb0.1Ho0.6Pr0.3(Fe0.8Co0.2)1.93 alloy, close to the anisotropy compensation point, has the largest magnetostriction and a low anisotropy at room temperature.

Studies on the magnetoelastic and magnetocaloric properties of Yb1−xMgxMnO3 using neutron diffraction and magnetization measurements

We report the magnetic ordering and magnetoelastic coupling of polycrystalline hexagonal Yb1−xMgxMnO3 (x = 0.00 and 0.05) compounds by using neutron diffraction measurements.

Macroscopic modeling of anisotropic magnetostriction and magnetization in soft ferromagnetic materials

Magnetic and magnetoelastic properties of soft ferromagnetic materials, used as laminated sheets, are sensitive to manufacturing processes such as rolling, cutting and coating. One of the effects of these processes is to induce an anisotropic behavior of materials. Therefore, an anhysteretic magnetostriction and magnetization calculation taking into account the anisotropy effect at macroscopic scale is presented. This model is based on the expression and then the minimization of the total energy in order to determine magnetization and magnetostriction at equilibrium. The total energy to minimize depends on energy terms identified from measurements of the magnetization and magnetostriction at a scale large enough to neglect the heterogeneity due to grains. Therefore, this approach attempts to reproduce ferromagnetic polycrystal behavior at macroscopic without knowing texture (Orientation Density Function) nor grain properties.

Magnetic actuator based on giant magnetostrictive material Terfenol-D with strain and temperature monitoring using FBG optical sensor

We have designed a temperature and strain monitoring system for a magnetic actuator based on the giant magnetostrictive material Terfenol-D (Tb0.3 Dy0.7Fe1.92) with Fiber Bragg grating (FBG) sensors. Magneto-elastic properties of Terfenol-D depend on magnetization, stress pre-history, and temperature. In order to simultaneously monitor these effects, we have implemented a system based on a cylindrical Terfenol-D rod monitored with four FBGs that allows making the appropriate compensations on the strain measurement due to temperature drift. We have measured the magnetostriction in the axial and the transverse directions for the Terfenol-D rod with two perpendicular FBGs, and calculated the Poisson ratio. An additional mechanical system for strain amplification has been designed in order to increase sensitivity, by a factor of 4, in the strain measurement with the FBG sensor.

Magnetic and magnetoelastic properties of valence transition compounds based on YbInCu4 (Review Article)

The intermetallic compound YbInCu4 undergoes an isostructural first-order valence-changing phase transition from a state with localized moments of the Yb into a Fermi liquid state with strong Kondo screening. This article reviews studies of the structure and of the electronic, magnetic, and magnetoelastic properties of compounds based on YbInCu4. The effects of alloying and pressure on such parameters of the electronic and magnetic state as the Kondo temperature, Curie paramagnetic temperature, effective magnetic moment, and valence of Yb are determined. The observational data are interpreted in terms of a single-impurity Kondo model. The magnetic anisotropy of single-crystal YbInCu4 and magnetostriction in high magnetic fields are studied. It is shown that a crystal field model for localized states of Yb3+ provides a good description of magnetic anisotropy and anisotropic magnetostriction in the high-temperature phase.

Structure, magnetism, and magnetostrictive properties of mechanically alloyed Fe81Ga19

In this work, structure–magnetic property correlations and the magnetostrictive response of mechanically alloyed powders of composition Fe81Ga19 were investigated using a variety of structural and magnetic probes. X-ray diffraction analysis of the as-milled powders suggests the presence of a chemically-disordered body-centered cubic phase. Thermal annealing of powder compacts results in formation of a secondary phase that demonstrates the cubic ordered L12 crystal structure. Magnetostriction measurements indicate that the magnetoelastic properties of the polycrystalline Fe81Ga19 compacts can be tailored by increasing the milling time duration followed by an anneal of the as-milled powders at 900 °C for 2 h in an Ar gas environment (O2 < 5 ppm). Under those conditions, the room temperature saturation magnetostriction was measured to be as high as 41 ppm at a low magnetic field of Happ ∼10 Oe. The magnetostrictive behavior of the mechanically alloyed Fe81Ga19 powders was found to be comparable with FeGa samples prepared by other non-equilibrium powder processing techniques. Based upon the results presented here, it is proferred that ball-milling offers a cost-effective pathway towards realizing large volumes of FeGa alloys having moderate values of magnetostriction.

Magnetoelastic properties of Co‐based amorphous ferromagnetic microwires

Vibrational magnetometry and small‐angle magnetization rotation methods have been used to study magnetoelastic properties of glass‐coated Co‐rich microwires of composition Co69Fe4Cr4Si12B11 with metallic nucleus diameter d = 55 μm and total diameter D = 80 μm. The saturation wire magnetization has been found to be Ms = 590 emu cm−3, the magnetostriction constant λs = −0.49 × 10−7, and the bare anisotropy field Ha = 0.24 Oe. The average value of the residual quenching stress has been estimated to be Δσ ≈ 137 MPa. The diagonal Zφφ component of the giant magnetoimpedance tensor turns out to be significantly dependent on the position along the wire axis. This can be attributed to a non uniformity of the residual stress distribution. It is shown that the measurement of the magnetic characteristics of the microwire enables one to estimate quantitatively the magnitude of the applied mechanical stress.

Study of magnetoelastic properties of pure nickel parts produced by metal injection moulding

Abstract The production of smart materials such as those with magnetoelastic properties is of increasing interest for some application as position transducers. The use of the metal injection moulding process permits the production of small parts with complex geometries as well as avoiding common defects produced by other processing techniques. In this study, a feedstock based on pure nickel and thermoplastic binder has been designed and moulded to have specific cylindrical geometry and defect-free green specimens. The parts were sintered changing several processing parameters that have influence on magnetoelastic effects. These effects were studied in terms of the field-dependent elastic modulus, which was estimated by subjecting the specimens to free longitudinal vibration while they remained within different magnetic fields from 0 to 2000 Oe. The optimal sintering parameters turned out to be 1325 °C for the temperature and 12 h for the holding time, whereas the estimated field-dependent elastic modulus variation (8%) was higher in comparison to variations in parts obtained by conventional processing (4%).

Second Order Precession in the Plate with Cubic Anisotropy and Magnetoelastic Properties

The paper considers the second order precession of the magnetization vector in a perpendicular magnetized anisotropic ferrite plate with magnetoelastic properties. The boundaries of the precession regimes on the frequency and amplitude of the alternating field were defined. The features of the precession of the magnetization vector regimes associated with magnetoelastic properties were revealed.

Magnetocaloric and Magnetoelastic Properties of the Gd&lt;sub&gt;5&lt;/sub&gt;Si&lt;sub&gt;2&lt;/sub&gt;Ge&lt;sub&gt;2&lt;/sub&gt; with Small Indium Substitutions in p-Sublattice

The purpose of this work was the complex investigation of magnetic, magnetocaloric and magnetoelastic properties of compounds based on Gd5Si2Ge2 with small In substitutions in p-sublattice. The conducted measurements revealed that both the magnetocaloric effect and the volume magnetostriction upon cooling reach the higher values than upon heating. Indium substitution leads to the appearance of the second maximum on the temperature dependence of the magnetocaloric effect resulting in the increase of the refrigerant capacity.