Maximum Magnetostriction Research Articles

Multifactorial impacts of B-doping on Fe81Ga19 alloys prepared by laser-beam powder bed fusion: Microstructure, magnetostriction, and osteogenesis

Magnetostrictive Fe-Ga alloys have captivated substantial focus in biomedical applications because of their exceptional transition efficiency and favorable cytocompatibility. Nevertheless, Fe-Ga alloys always exhibit frustrating magnetostriction coefficients when presented in bulk dimensions. It is well-established that the magnetostrictive performance of Fe-Ga alloys is intimately linked to their phase and crystal structures. In this study, various concentrations of boron (B) were doped into Fe81Ga19 alloys via the laser-beam powder bed fusion (LPBF) technique to tailor the crystal and phase structures, thereby improving the magnetostrictive performance. The results revealed the capacity for quick solidification of the LPBF process in expediting the solid solution of B element, which increased both lattice distortion and dislocations within the Fe-Ga matrix. These factors contributed to an elevation in the density of the modified-D03 phase structure. Moreover, the prepared Fe-Ga-B alloys also exhibited a 〈001〉 preferred grain orientation caused by the high thermal gradients during the LPBF process. As a result, a maximum magnetostriction coefficient of 105 ppm was achieved in the (Fe81Ga19)98.5B1.5 alloy. In alternating magnetic fields, all the LPBF-prepared alloys showed good dynamic magnetostriction response without visible hysteresis, while the (Fe81Ga19)98.5B1.5 alloy presented a notable enhancement of ∼30 % in magnetostriction coefficient when compared with the Fe81Ga19 alloy. Moreover, the (Fe81Ga19)98.5B1.5 alloy exhibited favorable biocompatibility and osteogenesis, as confirmed by increased alkaline phosphatase (ALP) activity and the formation of mineralized nodules. These findings suggest that the B-doped Fe-Ga alloys combined with the LPBF technique hold promise for the development of bulk magnetostrictive alloys that are applicable for bone repair applications.

Gallium induced effect on magnetic, magnetostrictive and electrical properties of sintered NiFe2O4

This study investigates how the incorporation of Ga ions into the tetrahedral coordination sites affects the magnetic, magnetostrictive, and electrical properties of sintered NiFe2O4. All characterization was performed on the sintered NiFe2-xGaxO4 samples, which were synthesized using the autocombustion method. The sintered samples exhibit a single phase, wherein the lattice parameter decreases, and the particle size increases with the augmentation of Ga-content within the Ni-ferrite lattice. Saturation magnetization (MS) was found to be higher for x = 0.25 compared to the parent sample (x = 0), while for x = 0.5, MS was slightly lower than that of the parent sample. Both coercivity (HC) and Curie temperature (TC) exhibited a decrease with increasing 'x,' which can be attributed to the weakening of superexchange interactions (A-O-B) due to the presence of non-magnetic Ga ions. Furthermore, the maximum magnetostriction (λmax) also decreased with increasing 'x,' reflecting a magnetic dilution effect within the system. Electric modulus analysis of the dielectric response and the Jonscher power law fits AC conductivity propounded the long-range hoping for charge transportation. Also, the Cole-Cole fit of impedance spectra showed a combined effect of electrode-grain boundary, grain interior, and grain-grain boundary.

Choosing the best magnetostrictive material for energy harvesting applications: A simple criterion based on Ericsson cycles

The best magnetostrictive material for energy harvesting applications is not necessarily the material with the highest magnetostriction strain. In this paper, based on the description of the Ericsson cycle, a simple criterion to define the most efficient material is proposed. The criterion takes into account the accessible range of stress and magnetic field. It relies on four material parameters only, namely the initial magnetic susceptibility, the saturation magnetisation, the maximum magnetostriction strain and the coercive field of the considered magnetostrictive material. Mass density and price are also involved if a weight optimisation or a cost optimisation is sought. The potential of several materials is compared based on this approach, and it is shown that Giant Magnetostrictive Materials are not systematically the best choice for energy harvesting applications, challenged for some operating conditions by electrical steels.

Role of Cu-substitution on microstructural, magnetic, magnetostrictive and dielectric properties of sintered NiFe2O4

This study examines the impact of Cu-amalgamation on the microstructural, magnetic, magnetostrictive, and dielectric properties of sintered nickel ferrite (NiFe2O4) ceramics. Without post synthesis calcination, the series of Ni1-xCuxFe2O4 (0 ≤ x ≤ 1) samples were synthesized via an autocombustion process with glycine (1 Mole/mole of metal ion) as a fuel. XRD analysis of the as-synthesized samples revealed that compositions up to x = 0.75 were phase pure. However, impurity CuFeO2 was detected in the x = 1 (CuFe2O4) sample, leading to its exclusion from further processing and testing. After sintering the compacted pellets (12 mm diameter and 3 mm thickness) at 1200 °C for 2 h, compositions up to x = 0.5 were confirmed as phase pure, prompting further characterization of these samples' structural, microstructural, magnetic, and dielectric properties. The unit cell dimension increased from 8.3268 Å for NiFe2O4 (x = 0) to 8.3560 Å for Ni0.5Cu0.5Fe2O4 (x = 0.50) due to the substitution of larger-sized ion (Cu2+) for the smaller-sized ion (Ni2+) in NiFe2O4. Notably, the addition of Cu facilitated substantial grain growth, as observed in the SEM micrographs, where the grain size increased from 556 nm for x = 0 to 13 μm for x = 0.5. As the Cu-content increased in Ni1-xCuxFe2O4, magnetic parameters such as TC (Curie temperature), K1 (Magnetocrystalline anisotropy constant), HC (Coercivity), and MS (Saturation magnetization) decreased. This decrease can be attributed to the replacement of the high-magnetic cation (Ni2+, 2 μB) with the low-magnetic cation (Cu2+, 1 μB) in the octahedral coordination site of NiFe2O4. The x = 0 and 0.5 samples exhibited a maximum magnetostriction strain (λmax) of ∽-35 ppm, and for x = 0.25 sample the value is −24 ppm. In terms of dielectric properties, the permittivity count of the x = 0 sample was higher than that of x = 0.25 and 0.5 samples in the lower frequency regime, likely due to a larger surface area (smaller grain size) contributing to significant surface polarization. Conversely, in the higher frequency regime, the samples with x = 0.25 and 0.5 demonstrated higher permittivity than the parent sample. The changes in dielectric behavior in the Cu-substituted samples were explained based on the microstructure of the samples.

Study on Enhanced Magnetostriction in (x)PbZr0.52Ti0.48O3-(1-x)NiFe2O4 Composites by Magnetoelectric Effect

Magnetoelectric composites (x)PbZr0.52Ti0.48O3(PZT)-(1-x)NiFe2O4 (NFO) with x values of 0.15, 0.30, 0.45, 0.55, 0.75, and 0.85 mol% were obtained by traditional solid phase reaction. The measured magnetic and magnetostriction properties are strongly dependent upon the molar fraction (1-x) of the NFO in the composites. The maximum magnetostriction coefficient of -52.4 ppm was observed in 0.3PZT-0.7NFO composite ceramic. All the magnetostriction in the composites is larger than the reported values. The larger magnetostriction would result from the magnetoelectric (ME) effect of the composites. We propose a model of the magnetostriction within the composites consisting of strain and polarization. The relationship between the ME effect and magnetostriction is discussed in the qualitative features of this model. This magnetoelectric composite material maintains a strong magnetostrictive effect, which can be used in multifunctional sensors. It will provide new ideas for the design of multifunctional sensors in the future.

Magnetostriction of Fe-rich FeSiB(P)NbCu amorphous and nanocrystalline soft-magnetic alloys

The compositional effect of magneto-elastic and magnetostriction properties of Fe-rich Fe81B15−xPxSi2Nb1Cu1 (ii) Fe82B14−xPxSi2Nb1Cu1 and (iii) Fe83B13−xPxSi2Nb1Cu1 (x = 0, 4, 8) amorphous and annealed nanocrystalline alloy ribbons were investigated. The present study adds knowledge to the limited magnetostriction literature available for Fe-rich nanocrystalline alloys by systematically varying the Fe and P content. A combination of Becker-Kersten and small angle magnetization rotation (SAMR) techniques has been employed for the magnetostriction (λs) evaluation. Both the as-quenched and nanocrystalline ribbons exhibit large positive magnetostriction and show strong compositional dependence to the P content. In the as-quenched condition, 4 at% P addition shows maximum magneto-elastic response and magnetostriction constant, with Fe81B11P4Si2Nb1Cu1 alloy exhibiting a maximum of + 52 ppm and P-free Fe83B13Si2Nb1Cu1 alloy exhibiting a minimum of + 27 ppm. In the nanocrystalline state, a slight reduction of magnetostriction is seen for all alloys, with a maximum of + 32 ppm (4 at% P) and a minimum of + 22 ppm (P-free) in Fe83 at% alloys. The unusual large magnetostriction of optimally annealed samples is attributed to the relatively low crystal volume fraction (30–45%) of nanocrystalline ribbons. The lowest magnetostriction of Fe83B13Si2Nb1Cu1 alloy in both as-quenched and annealed state is explained based on ribbon structural heterogeneity consisting of crystal nuclei and textured α-Fe surface crystallization. The study reveals a contradictory response of magneto-crystal anisotropy (grain size reduction) and magneto-elastic anisotropy to the P addition and ribbon structural heterogeneity. The study discusses the implications of the large magneto-elastic anisotropy associated with Fe-rich nanocrystalline ribbons and the way forward for improving their magnetic softness.

Количественный анализ текстуры деформации и первичной рекристаллизации при угловой прокатке и отжиге магнитострикционного сплава (Fe83Ga17)99B1

The Fe–Ga alloy is a promising magnetostrictive material thanks to of the optimal combination of functional properties and relatively low price due to the absence of rare-earth elements in the composition. To obtain the maximum magnetostriction in Fe–Ga polycrystals, it is necessary to create a crystallographic texture with a predominance of the <100> direction, since the tetragonal magnetostriction constant is the largest. Traditional methods of thermomechanical treatment do not lead to the formation of such a texture in a bcc alloy. In this paper, for the first time, the authors propose to use inclined rolling to increase the proportion of favorable texture components. Warm rolling with a deformation degree of 70 % was carried out at angles of 0, 30 and 90° to the direction of hot rolling. The deformation texture was examined using X-ray texture analysis and the texture and structure of the material after recrystallization was analyzed by electron backscatter diffraction (EBSD) on a scanning electron microscope. Quantitative texture analysis was carried out using the orientation distribution function (ODF) method using the ATEX software. The volume fraction of some texture components was calculated. The study shows that a significant change in the deformation textures and primary recrystallization occurs during rolling at an angle of 90°. The sample after such rolling contains the largest amount of the planar component {100}. The study identified a relationship between the texture of deformation and recrystallization in Fe–Ga: to increase the proportion of components with the <001> crystallographic direction during recrystallization, the presence of planar components {111} in the deformation texture is necessary, which is associated with the predominant growth of favorable components in the deformation matrix with such a texture.

Secondary recrystallization of {310} texture and enhanced magnetostriction in Fe–Ga alloy thin sheet

Sharp {310}<001> texture and enhanced magnetostriction were achieved in Fe–Ga thin sheets by secondary recrystallization. The evolution of texture, inhibitor, and magnetostriction of Fe–Ga thin sheet during the annealing process were analyzed. A fine and homogeneous microstructure with a strong γ-fiber and weak Goss and {310}<001> texture was produced. Goss and {310}<001> texture did not exhibit any advantage in terms of the grain size and number over the matrix grains in the primary recrystallization, but {310}<001> texture is superior to Goss texture in grain size and number. Statistical results show that a large number of MnS and NbC precipitates with the size range of 20–140 nm dispersedly distributed in the primary matrix grains thus inhibiting the normal grain growth of primary grains sufficiently. The microstructure and texture evolution during the annealing process indicates that the secondary recrystallization of {310}<001> texture is related to the combination of grain size, quantity, and high energy grain boundary characteristic of {310}<001> texture. The secondary recrystallization of {310}<001> texture is conducive to the improvement of the magnetostrictive coefficient and a maximum magnetostriction of 240 ppm was obtained in Fe–Ga thin sheet after final annealing.

Secondary Recrystallization Texture and Magnetostriction in Fe-Ga Alloy Ultra-Thin Sheet

The 0.15 mm thick Fe-Ga alloy ultra-thin thin sheets with high magnetostriction were successfully produced by the conventional processing route including hot rolling and two-stage cold rolling with intermediate annealing and primary and secondary recrystallization annealing. The evolution of microstructure, texture, and inhibitor was briefly investigated. The primary recrystallization texture is characterized by strong <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula> fiber with the peak at {111} <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\langle 112\rangle $ </tex-math></inline-formula> component and weak Goss component through sheet thickness. The dispersedly distributed nano-precipitates provide a sufficient pinning effect on the primarily recrystallized grains and induce abnormal grain growth of Goss grains. Well-developed secondary recrystallized Goss grains with centimeter size and maximum magnetostriction (3/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\lambda \text{s}$ </tex-math></inline-formula> ) of 229 ppm were achieved in Fe-Ga alloy ultra-thin sheet.

Non-contact torque sensor based on magnetostrictive Fe30Co70 alloy

A non-contact torque sensor based on a magnetostrictive Fe30Co70 rod wound with an excitation coil and a pickup coil is proposed in this paper. In the magnetic field range 0–30 kA/m, the changing rate and linearity of magnetostriction with a loading magnetic field of Fe30Co70 samples are significantly improved after heat treatment. Maximum magnetostriction is 103 ppm in the annealed sample in the parallel direction, while its tensile strength and allowable shear stress are 608 and 194.56 MPa, respectively. According to the mathematical model presented in this work, there is a linear relationship between the output voltage and torque. An apparent increase in the induced voltage signal (peak voltage) of 48.23 mV is observed as the torque increases to 20 Nm in the case of applying sinusoidal excitation signals. In addition, the experimental results are consistent with the calculated values within the torque range 0–16 Nm, and a good sensitivity of 2.87 mV/Nm is obtained. This work shows the prospect of Fe30Co70 alloy for non-contact torque sensing for the appropriate magnetostrictive property with no orientation requirement.

Magnetostriction and damping of forced vibrations in Fe-Cr-Mo-Al alloy

The magnetostriction, damping capacity and mechanical properties of a Fe-Cr-Mo-Al alloy are studied and compared with binary Fe-Cr and Fe-Al alloys. Synchronous change in magnetostriction and damping in Fe-16Cr-0.6Mo-0.6Al alloy: the maximum magnetostriction strain and damping capacity are obtained after annealing at 900 °C followed by air cooling. Frequency dependence of damping in subresonance range is analyzed and interpreted in terms of variations in relaxation time and stiffness of DMA.

Effect of defects on magnetostriction and magnetic moment evolution of iron thin films

Magnetostrictive materials have broad application prospects in sensing, control, energy conversion, and information conversion. The improving of the performances and applications of such materials has become a research hotspot, but defects will inevitably appear in the preparation and use of materials. In this study, the magnetostrictive structure model of iron elemental material with no defect or hole defect or crack defect is established by the molecular dynamics method. The influences of different defects on the magnetostrictive behavior of iron thin films are analyzed, and the mechanism of the influence of defects on the magnetostrictive behavior is depicted from the perspective of atomic magnetic moment. The results show that the films with 60 × 2 × 1 defects in the center are the easiest to reach saturation magnetostriction, and the magnetostriction is the least after reaching saturation, with respect to the films without defects. The films with 10 × 10 × 1 and 2 × 60 × 1 defects in the center require a larger magnetic field to approach to saturation, and the magnetostriction of the film with 2 × 60 × 1 defects in the center reaches a maximum value after saturation. This is because the defects will affect the magnetic moment of the surrounding atoms and make them deflect to the direction parallel to the defects, thus affecting the magnetostriction of the iron thin film. Among them, the hole defects have less influence on the magnetostriction, while the crack defects have stronger influence on the magnetostriction. The direction of the crack also has an effect on the magnetostriction of Fe thin film. When the crack is parallel to the direction of magnetization, the maximum magnetostriction of the film in the direction of magnetization from the initial state to the saturation of magnetization will decrease. When the crack is perpendicular to the direction of magnetization, the maximum magnetostriction of the film in the direction of magnetization from the initial state to the saturation of magnetization will increase. These results suggest that the defects affect the magnetostriction of the model as a whole during magnetization by affecting the initial magnetic moment orientation of the surrounding atoms.

Secondary recrystallization behavior in magnetostrictive Fe-Ga thin sheets induced by nano-sized composite precipitates

Strengthening η texture (⟨001⟩//rolling direction) through secondary recrystallization can significantly improve the magnetostriction coefficient of Fe-Ga thin sheets and expand the use of Fe-Ga alloys in high-frequency applications. However, the secondary recrystallization of Goss texture in Fe-Ga thin sheets deteriorates significantly with the thinning of the sheet thickness under the current inhibitors of micron-sized NbC particles or precipitates. In this paper, a new composite inhibitor system, composed of nano-sized MnS and Nb(C,N) precipitates, is proposed to induce the secondary recrystallization Goss texture in Fe-Ga thin sheets with thicknesses less than 0.3 mm. The density and size of MnS and Nb(C,N) is designed based on the effect of alloy composition and hot rolling parameters on the precipitation kinetics of MnS and Nb(C,N), including the relative nucleation rate-temperature (NrT) and precipitation-time-temperature (PTT) curves. It is found that the stored deformation energy increases the maximum nucleation rate and the fastest precipitation temperature. A large number of lamellar and rectangular precipitates (MnS and Nb(C,N)) with a size of 5∼20 nm were precipitated after hot-rolling at a temperature of 800∼1,050 °C and a total thickness reduction of 80%. These nano-sized inhibitors provide a strong pinning effect for the primary recrystallized grains, and induce abnormal grain growth of Goss grains at an annealing temperature of 950∼1,050 °C. Resultingly, centimeter-sized Goss grains with a small deviation angle and maximum magnetostriction coefficient of 264 ppm are successfully achieved in Fe-Ga alloy thin sheets with a thickness of 0.25 mm.

Role of Mg2+ and In3+ substitution on magnetic, magnetostrictive and dielectric properties of NiFe2O4 ceramics derived from nanopowders.

The effect of Mg2+ and In3+ substitution on the structural, magnetic, magnetostrictive and dielectric properties of NiFe2O4 samples derived through sintering of nanocrystalline ceramic powders is investigated. Namely, NiFe2O4, NiMg0.2Fe1.8O4 and NiIn0.2Fe1.8O4 nanopowders were synthesized by a tartrate-gel route followed by calcination at 500 °C, pelletization and sintering at 1200 °C for 2 h. The average particle size was found to decrease from ∼13 nm (for NiFe2O4) to ∼9 nm and ∼7 nm for as-synthesized Mg2+ and In3+ substituted NiFe2O4 samples (after calcination), respectively. However, after sintering a better grain growth occurs for the In3+ substituted sample, as confirmed through the microscopy and dielectric results. Due to the replacement of smaller Fe3+ cations by larger In3+ and Mg2+ cations at the tetrahedral (Td) and octahedral (Oh) interstitial positions, respectively, in the spinel structure of NiFe2O4, the lattice parameters increase in both the cases. The Td site occupation of In3+ leads to higher magnetization for the NiIn0.2Fe1.8O4 sample, but Oh site occupation of Mg2+ leads to lower magnetization for the NiMg0.2Fe1.8O4 sample, in comparison to the pure NiFe2O4 sample. Furthermore, the Curie temperatures (TC) and magnetocrystalline anisotropy constants (K1) for both the samples are considerably lower than the parent compound, with all the parameters being the lowest for the In3+ substituted sample because the Td occupation of non-magnetic In3+ drastically decreases the A-O-B magnetic superexchange interactions. The above alteration to the magnetic interactions alters the magnitude of maximum magnetostriction (λmax), which is explained based on the occupation of the Mg2+ and In3+ cations in our samples. The obtained magnetostriction properties of our samples are very useful for magnetostriction based sensor application.

Enhanced magnetostrictive properties of lightly Pr-doped Fe83Ga17 alloys

Fe83Ga17Prx alloys, where x = 0, 0.2, 0.4, 0.6 and 1.0, were prepared by a non-consumable vacuum arc melting technique under an inert argon gas atmosphere. The crystal structure and surface morphologies of the alloys were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Local compositional variations were measured by energy dispersive X-ray spectroscopy (EDXS). The magnetostriction coefficients of the alloys were measured by means of a differential resistive strain sensor. The magnetism of the sample was measured by a vibrating sample magnetometer (VSM). The results show that the parent Fe83Ga17 alloy consists of a single A2 phase of bcc symmetry, whereas the Pr doped Fe83Ga17 alloys are composed of the A2 phase of bcc structure and a small volume fraction of PrGa2 as a secondary phase. Most importantly, with increasing x, the magnetostriction coefficient of the Fe83Ga17Prx alloys first increases reaching a maximum saturation magnetostriction coefficient of 192 ppm for x = 0.6 at a magnetic field strength of 486 kA/m, then decreased. This maximum represents a 400% increase over the parent alloy with a mere 0.6 at% Pr doping.

Bulklike behavior of magnetoelasticity in epitaxial Fe1−xGax thin films

Bulk ${\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Ga}}_{x}$ alloys present a strong sensitivity of the magnetostrictive properties with Ga content with maximum magnetostriction near $x=0.19$. Here, we present magnetoelastic coefficients measured by the cantilever method on ${\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Ga}}_{x}$ thin films grown by molecular beam epitaxy on GaAs(001). We find that Ga-dependent magnetoelastic coefficients in nanometer thin films are comparable in magnitude to the respective bulk values. Moreover, we compare thin films with a tetragonal structure due to a slightly preferential alignment of Ga pairs along the growth direction with and a cubic structure. It turns out that magnetoelastic coefficients are unaffected by a preferential alignment of Ga pairs along the growth direction.

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.

Non‐Destructive Surface Energy Measurements on (1 0 0) Galfenol

AbstractDeveloping protocols for making thin sheet FeGa (Galfenol) with abnormally grown Goss or Cube grains, which provide maximum magnetostriction, is challenging because the mechanisms that regulate grain boundary mobility and texture development in these alloys are not yet understood. Grain boundary energy models do not account for forces caused by the control of surface energy from atmospheric annealing conditions. By characterizing the surface energy of specific Galfenol grains, we can develop a more accurate thermodynamic framework for modeling abnormal grain growth and texture development. To non‐destructively measure surface energy of specific crystal orientations and overcome passivation layer difficulties in previous studies, a two‐liquid‐phase contact angle method is utilized. A single‐crystal (1 0 0) Fe82Ga18 is used as a proof of concept for its isotropic surface crystal orientation. The resultant contact angle data shows a high dependence on the use of Ar‐plasma surface preparation to remove native oxides exposing a true interaction between a sessile drop and the Galfenol surface. Experimentally measured surface energy values are in agreement with density functional theory simulations. Surface texture and composition are confirmed using EBSD and XPS measurements. This non‐destructive technique paves the way towards studying surface energies of bare metal surfaces.

Large enhancement in the magnetostriction parameters of the composite of CoFe2O4 and CoFe1.9Ga0.1O4

A new strategy to enhance the magnetostriction parameters of cobalt ferrite (CoFe2O4) is illustrated. A composite comprising of nanocrystalline CoFe2O4 and bulk CoFe1.9Ga0.1O4 powders were mixed together then compacted and sintered at 1450 °C for 10 min. For a composite of 70 wt% CoFe2O4 and 30 wt% of CoFe1.9Ga0.1O4, maximum magnetostriction coefficient (λmax) of −350 ppm has been obtained at lower magnetic field which is nearly 20% and 65% higher than that obtained for CoFe2O4 and CoFe1.9Ga0.1O4, respectively. Moreover, the composite exhibited higher strain sensitivity [dλ/dH]max of −2.6 × 10−9 A−1 m against the individual components of the composite.

Single Goss grain growth by isothermal annealing in rolled Fe–Al–Ga–NbC sheets

The (Fe82Al13.5Ga4.5)99.9(NbC)0.1 sheets with strong Goss texture and large magnetostriction were prepared by rolling and isothermal annealing processes. Single Goss grain growth was observed in sheets undergoing isothermal annealing at 1050 °C for 1 h using Ar as protecting gas. With annealing time increasing to 8 h at 1050 °C, a largest magnetostriction of 154 × 10−6 is obtained in sheet and a large λ// (the maximum magnetostriction with magnetic field parallel to rolling direction) of 160 × 10−6 along the rolling direction is also observed. The fact that a λ// of 160 × 10−6 along RD can be achieved with only 4.5 at% Ga in the Fe-18 at% (Al, Ga) sheet is of practical importance. Compared with previous studies in Fe–Al and Fe–Ga sheets, this paper provides a more efficient approach to prepare strong Goss textured sheets. In this way, a slow continuous heating process, sulfur-induced surface energy control and high-temperature annealing above 1200 °C are no more necessary. It shows a good prospect for industrial production of high-performance magnetostrictive alloy sheets.