Magnetoelastic Effects Research Articles

Dynamic magnetoelastic properties of TbxHo0.9−xNd0.1(Fe0.8Co0.2)1.93/epoxy composites

Abstract TbxHo0.9−xNd0.1(Fe0.8Co0.2)1.93/epoxy (0 ⩽ x ⩽ 0.40) composites are fabricated in the presence of a magnetic field. The structural and dynamic magnetoelastic properties are investigated as a function of both magnetic bias field Hbias and frequency f at room temperature. The composites are formed as textured orientation structure of 1–3 type with 〈1 0 0〉 preferred orientation for x ⩽ 0.10 and 〈1 1 1〉-orientation for x ⩾ 0.25. The composites generally possess insignificant eddy-current losses for frequency up to 50 kHz, and their dynamic magnetoelastic properties depend greatly on Hbias. The elastic modulus (E3 H and E3 B) shows a maximum negative ΔE effect, along with a maximum d33, at a relatively low Hbias ~ 80 kA/m, contributed by the maximum motion of non-180° domain-wall. The 1–3 type composite for x ⩾ 0.25 shows an enhanced magnetoelastic effect in comparison with 0 to 3 type one, which can be principally ascribed to its easy magnetization direction (EMD) towards 〈1 1 1〉 axis and the formation of 〈1 1 1〉-texture-oriented structure in the composite. These attractive dynamic magnetoelastic properties, e.g., the low magnetic anisotropy and d33 , max as high as 2.0 nm/A at a low Hbias ~ 80 kA/m, along with the light rare-earth Nd element existing in insulating polymer matrix, would make it a promising magnetostrictive material system.

Evaluation of the inverse magnetostrictive effect in heat‐treated Fe‐Co wire/polymer composites

Evaluation of the inverse magnetostrictive effect in heat‐treated Fe‐Co wire/polymer composites

Performance boost of co-rich fe-co based alloy magnetostrictive sensors via nitrogen treatment

The inverse magnetostrictive response (i.e. a change in magnetization due to an applied stress) of magnetostrictive materials, the Villari effect is widely applied for sensor applications. Mechanical properties are an important factor when applied for vibration energy and sensor applications. Surface-treatment methods are widely used for enhanced performance and serviceability of engineering components, and nitriding is one of the most versatile surface engineering method nowadays. These methods allow the fine tuning of surface quality-dependent properties such as the resistance to fatigue, wear, and corrosion. In this study, the change of inverse magnetostrictive characteristics of Co-rich Fe-Co bimetals by the nitriding treatment, for 30 min at 580 °C, was evaluated. The effect of the nitriding treatment on the inverse magnetostrictive characteristics, magnetostrictive susceptibility and magnetic hysteresis loop of Fe-Co bimetals, by an applied load, were evaluated by three-point bending tests under a magnetic field. Furthermore, the output voltage of the as-rolled Fe-Co/Ni bimetal and the nitrided Fe-Co/Ni bimetal cantilevers, under bending vibration, were compared. The nitride Fe-Co/Ni bimetal construct exhibited a high output voltage compared to the as-rolled Fe/Ni bimetal.

Rectification of Spin Current in Inversion-Asymmetric Magnets with Linearly Polarized Electromagnetic Waves

We theoretically propose a method of rectifying spin current with a linearly polarized electromagnetic wave in inversion-asymmetric magnetic insulators. To demonstrate the proposal, we consider quantum spin chains as a simple example; these models are mapped to fermion (spinon) models via Jordan-Wigner transformation. Using a nonlinear response theory, we find that a dc spin current is generated by the linearly polarized waves. The spin current shows rich anisotropic behavior depending on the direction of the electromagnetic wave. This is a manifestation of the rich interplay between spins and the waves; inverse Dzyaloshinskii-Moriya, Zeeman, and magnetostriction couplings lead to different behaviors of the spin current. The resultant spin current is insensitive to the relaxation time of spinons, a property of which potentially benefits a long-distance propagation of the spin current. An estimate of the required electromagnetic wave is given.

Strain-induced reversible manipulation of orbital magnetic moments in Ni/Cu multilayers on ferroelectric BaTiO3

Controlling magnetic anisotropy by orbital magnetic moments related to interfacial strains has considerable potential for the development of future devices using spins and orbitals. For the fundamental physics, the relationship between strain and orbital magnetic moment is still unknown, because there are few tools to probe changes of orbital magnetic moment. In this study, we developed an electric field (E)-induced X-ray magnetic circular dichroism (EXMCD) technique to apply E to a ferroelectric BaTiO3 substrate. We reversibly tuned the interfacial lattice constants of Ni/Cu multilayers on BaTiO3 using this technique. As the domain structures in BaTiO3 are modulated by E, EXMCD measurements reveal that the changes in the magnetic anisotropy of Ni/Cu films are induced through the modulation of orbital magnetic moments in Ni with magneto-elastic contributions. The strained Ni layer that induces the perpendicular magnetic anisotropy without E is released at E = 8 kV/cm, and in-plane magnetization also occurs. We observed that EXMCD measurements clarified the origin of the reversible changes in perpendicular magnetic anisotropy and established the relationship between macroscopic inverse magnetostriction effects and microscopic orbital moment anisotropy.

Ab initiotheory of the Gibbs free energy and a hierarchy of local moment correlation functions in itinerant electron systems: The magnetism of theMn3Amaterials class

Phase diagrams and the temperature and field dependence of complex magnetic materials are described here by an $a\phantom{\rule{0}{0ex}}b\phantom{\rule{0.333em}{0ex}}i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o$ theory. Consideration of fluctuating local degrees of freedom (`local moments'), emerging from a material's interacting itinerant electrons, produces naturally a picture of multisite magnetic interactions. Accurate prediction of the order of transitions and the role of both electronic and magnetoelastic effects in the Gibbs free energy coefficients are demonstrated by application to the widely varying frustrated magnetism of Mn${}_{3}$$A$ .

Controllable magnetic anisotropy of ferromagnet/antiferromagnet bilayers coupled with piezoelectric strain

Coupling of magnetoelastic and piezoelectric effects is achieved with the ferromagnetic (FM) Co60Fe20B20/antiferromagnetic (AFM) Co0.7Ni0.3O bilayers deposited on the surface of piezoelectric single crystalline substrate. Piezoelectric strain of the substrate is successfully transferred to the magnetic layers, and controllable variation of magnetic anisotropy in response to the elastic deformation is demonstrated in the M-H loops measured at various azimuthal angles with respect to the direction of AFM spin alignment. Magnetic behaviors of the exchange coupled bilayers can be understood by considering the competition of many magnetic anisotropy energies within the magnetic film based on the modified Meiklejohn and Bean (MB) model. From the comparison of experimentally measured results with the modified MB model, it is found that the strain in the film from the substrate effectively introduces additional uniaxial anisotropy in the FM layer with its anisotropy direction and magnitude determined by the applied strain.

CoFeB/MgO-based magnetic tunnel junction directly formed on a flexible substrate

We succeeded in fabricating a CoFeB/MgO-based magnetic tunnel junction (MTJ) directly on an organic flexible substrate. The MTJ shows good strain endurance while keeping the tunnel magnetoresistance (TMR) ratio of ∼100% under various strained conditions; the TMR ratio is almost unchanged up to a tensile strain of 1.2%. Because of the magnetoelastic effect, the magnetic anisotropy fields for the top and bottom CoFeB layers are linearly proportional to strain with almost the same rate as that in a single CoFeB film, suggesting that the expected strain is added on both CoFeB layers in the MTJ pillar from the stretched flexible substrate.

Applications and Advances of Magnetoelastic Sensors in Biomedical Engineering: A Review.

We present a comprehensive investigation into magnetoelastic sensors (MES) technology applied to biomedical engineering. This includes the working principles, detection methods, and application fields of MES technology. MES are made of amorphous metallic glass ribbons and are wireless and passive, meaning that it is convenient to monitor or measure the parameters related to biomedical engineering. MES are based on the inverse magnetoelastic (Villari) effect. When MES are subjected to mechanical stress, their magnetic susceptibility will change accordingly. And the susceptibility of MES is directly related to their magnetic permeability. The varying permeability can positively reflect the applied stress. The various detection methods that have been developed for different field applications include measurement of force, stress, and strain, monitoring of various chemical indexes, and consideration of different biomedical parameters such as the degradation rate and force conditions of artificial bone, as well as various physiological indexes including ammonia level, glucose concentration, bacteria growth, and blood coagulation.

Microstructure evolution and magnetic properties of annealed magnetostrictive Fe81Al19 coatings and their ultrasonic guided wave transducing performance

The microstructure, magnetic and magnetostrictive properties as well as ultrasonic guided wave sensing performance of annealed Fe81Al19 coatings prepared on 316L stainless steel by high velocity oxy-fuel spraying were investigated systematically. The maximum magnetostriction reaches 38 ppm with the coating annealed at 400 °C and the saturation magnetic field is <400 Oe. The phase transformation behavior of A2 → A2 + DO3 occurs with the annealing temperature increases above 470 °C. Effects of annealing on texture and structural evolution and magnetic properties of the coating are also discussed. Based on magnetostrictive effect and Villari effect of Fe81Al19 coating, the ultrasonic guided waves are actuated and detected successfully. With proper bias magnetic field, the amplitudes of echo signals can be enhanced in Fe-Al coating annealed at 500 °C. The corresponding (dλ/dH)max under a lower bias magnetic field indicates less eddy current loss and the optimal transduction. The deeper electromagnetic skin depth in the annealed coating results in a higher ultrasonic guided wave amplitude and improves the detection sensitivity in the electromagnetic acoustic transducers. This work exhibits the prospect of the magnetostrictive coatings in a range of potential applications, such as electromagnetic acoustical transducers used for non-destructive testing.

Phase separation and surface segregation in Co–Au–SrTiO3 thin films: Self-assembly of bilayered epitaxial nanocolumnar composites

Phase separation and surface segregation are powerful levers that allow one to synthesize nanocomposites via self-assembly. In the present work, we combine these concepts with vertical epitaxial growth and study Co-Au-${\mathrm{SrTiO}}_{3}$ thin films as a model system. We demonstrate that ${\mathrm{SrTiO}}_{3}$, Co, and Au undergo phase separation during sequential pulsed laser deposition, giving rise to a dense array of ultrathin bilayered Co-Au nanowires (NWs) with highly anisotropic optical and magnetic properties. A detailed analysis of the structure of the embedded metallic NWs reveals stabilization of a Co fcc phase and pronounced coupling to the matrix, which leads to large magnetoelastic effects. We discuss possible growth mechanisms yielding bilayer phase separation in nanocolumnar composites and show how the present results can be used to estimate a lower bound for the Co-Au interface energy.

Giant Magneto-Elastic and Magneto-Volume Effects in Fe–Al

This Letter reports large room-temperature non-Joulian magneto-strains of ∼3400 ppm and simultaneously large volume changes of ∼1300 ppm in Fe–Al; this occurs at low energy losses (coercivity <0.2 ...

Wireless and Passive Magnetoelastic-Based Sensor for Force Monitoring of Artificial Bone

A novel magnetoelastic-based sensor (MBS) is proposed in this paper to monitor the force of artificial bone (AB) using magnetoelastic material as the sensing element based on the inverse magnetoelastic effect. The MBS is embedded inside the AB using novel 3-D printing technology (N3DPT). Seven ABs are fabricated by N3DPT and tested by self-developed experimental devices to select the optimum output position of MBS and explore the relationship between the external force working on the AB and the varying value of output power (VOP) caused by the MBS. The applied force of the AB covered by biological tissue is also further monitored using MBS. Results indicate that the middle position ( $h=0$ ) of the AB can fully express the performance of MBS and clearly reflect and monitor the applied force of the AB using a wireless and passive method. An increase of external force working on the AB can cause a rise in output power of the sensing coil which is 0.5 dbm of the VOP under 100 N external force. This further demonstrates that the MBS can efficiently monitor the force of AB and prosthesis in vitro and in vivo .

Preface to Special Issue on Magneto-Elastic Effects

Preface to Special Issue on Magneto-Elastic Effects

Magnetoelastic Effects in Doubly Clamped Electroplated Co77Fe23 Microbeam Resonators.

Magnetostrictive Co77Fe23 films are fully suspended to produce free-standing, clamped-clamped, microbeam resonators. A negative or positive shift in the resonant frequency is observed for magnetic fields applied parallel or perpendicular to the length of the beam, respectively, confirming the magnetoelastic nature of the shift. Notably, the resonance shifts linearly with higher-bias fields oriented perpendicular to the beam's length. Domain imaging elucidates the distinction in the reversal processes along the easy and hard axes. Together, these results suggest that through modification of the magnetic anisotropy, the frequency shift and angular dependence can be tuned, producing highly magnetic-field-sensitive resonators.

Anisotropic magnetodielectric coupling in antiferromagnet Co4Nb2O9

The magnetodielectric effect has been investigated for single crystals of a honeycomb antiferromagnet Co4Nb2O9. In addition to large magnetoelectric coupling, a magnetodielectric response was observed in the antiferromagnetic phase, which is anisotropic with respect to the direction of the external magnetic field within the basal plane. To explain the anisotropy, we examined the magnetoelastic effect and found that the honeycomb is elongated along the magnetic field direction but shrunk along the perpendicular axis. The distortion should cause the change in the force constant, leading to a variation of permittivity in the presence of a magnetic field.

Magnetostriction theory of ultrathin freestanding nanofilms

In this paper, a continuum theory for describing the magnetostrictive behavior of magnetic nanofilms is proposed. Surface effects (including surface elastic and surface magnetoelastic effects) as well as symmetry lowering of nanofilms are considered in the theoretical scheme. The spherical symmetry is lowered to the cylindrical one in nearly two-dimensional nanofilms. And then, there are some additional new elastic and magnetoelastic parameters induced by symmetry lowering have to be reckoned into model the magnetostriction of nanofilms rigorously. The application of our theoretical scheme to Fe nanofilms shows good agreement with experiment. The magnetostriction minimum vs film thickness of Fe nanofilms was produced straightforwardly. In addition, the surface elastic and surface magnetoelastic constants are physically reasonable and consistent with most solid surfaces (on the order of 1–10 J/m− 2 for surface elasticity and 10− 2–10− 4 J/m− 2 for surface magnetoelasticity). This fact confirms the great importance of additional new elastic and magnetoelastic parameters in magnetostriction theory of magnetic nanofilms. The relationship (λx = − 2λy = − 2λz) between magnetostrictions breaks down for nanofilms. In addition, when the magnetic field is applied along vertical direction, the magnetostriction of nanofilms behaves different from the case that magnetic field is applied along in-plane direction.

Magnetostrictive vibrational power generator for battery-free IoT application

This study proposes a novel vibrational power generator based on magnetostrictive material (Fe–Ga alloy) for battery-free Internet of Things (IoT) applications. The device consists of a U-shaped magnetic frame with one leg forming a unimorph comprising a bonded Fe–Ga alloy plate and magnetic material, with a coil wound over the unimorph and a permanent magnet placed between the two legs of the frame. Via magnetically saturating the part of the frame at the point where the Fe–Ga plate is bonded, an electromotive force is generated in the coil by vibrations according to the change in the magnetic flux of the Fe–Ga alloy as generated by the inverse magnetostrictive effect. The device is simple in structure, highly robust, and affords an ease of assembling that is suitable for mass production. We also evaluate a prototype device (device weight of 4 g) using an Fe–Ga plate with dimensions of 4 × 0.5 × 16 mm. With a weight of 1.7 g attached to the device, an open-circuit voltage of 4 V at an oscillation frequency of 88.7 Hz and acceleration of 6.0 m/s2 yields an effective power of 2.0 mW. With a weight of 10.2 g, an effective power of 0.39 mW is generated at a frequency of 28.4 Hz and acceleration of 0.73 m/s2. After 100 million repeated oscillations at 420 Hz and 78.4 m/s2, the resonant frequency and voltage remain unchanged. The device performance is sufficient to replace the button cell used in wireless modules. Further, in order to examine the device feasibility, I investigate two applications related to short-distance (sending ON signals) and long-distance (sending data of temperature and vibration frequency) wireless sensors driven by the proposed device.

Tracking picosecond strain pulses in heterostructures that exhibit giant magnetostriction.

We combine ultrafast X-ray diffraction (UXRD) and time-resolved Magneto-Optical Kerr Effect (MOKE) measurements to monitor the strain pulses in laser-excited TbFe2/Nb heterostructures. Spatial separation of the Nb detection layer from the laser excitation region allows for a background-free characterization of the laser-generated strain pulses. We clearly observe symmetric bipolar strain pulses if the excited TbFe2 surface terminates the sample and a decomposition of the strain wavepacket into an asymmetric bipolar and a unipolar pulse, if a SiO2 glass capping layer covers the excited TbFe2 layer. The inverse magnetostriction of the temporally separated unipolar strain pulses in this sample leads to a MOKE signal that linearly depends on the strain pulse amplitude measured through UXRD. Linear chain model simulations accurately predict the timing and shape of UXRD and MOKE signals that are caused by the strain reflections from multiple interfaces in the heterostructure.

Multilevel information storage using magnetoelastic layer stacks

The use of voltages to control magnetisation via the inverse magnetostriction effect in piezoelectric/ferromagnet heterostructures holds promise for ultra-low energy information storage technologies. Epitaxial galfenol, an alloy of iron and gallium, has been shown to be a highly suitable material for such devices because it possesses biaxial anisotropy and large magnetostriction. Here we experimentally investigate the properties of galfenol/spacer/galfenol structures in which the compositions of the galfenol layers are varied in order to produce different strengths of the magnetic anisotropy and magnetostriction constants. Based upon these layers, we propose and simulate the operation of an information storage device that can operate as an energy efficient multilevel memory cell.