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• Study of spin dynamics in Ta/NiFe/FeMn/CoFeB multilayer by varying NiFe thickness. • Two distinct FMR modes are found for the NiFe and CoFeB layers. • The separation between the resonance fields shows reconfigurable phenomena. • Parallel mode spin-to-charge conversion is explored using the ISHE technique. • NiFe layer significantly contributes to spin-to-charge conversion. The precise engineering of microwave absorption frequencies is of paramount importance in the advancement of spintronic-based RF devices. In the pursuit of this objective, magnetic thin films demonstrate unrivaled efficacy in enabling external modulation of their microwave responses in a reconfigurable manner. Here, we demonstrate dual-frequency ferromagnetic resonance modes and corresponding spin-to-charge conversion efficiency in thin film structures comprising Ta/NiFe/FeMn/CoFeB multilayer. A systematic thickness variation of the NiFe layer (i.e., 4–20 nm) has been undertaken to elucidate the impact on both static and dynamic properties across the multilayer structure. The presence of two distinct magnetic layers manifests in the emergence of two-step magnetic hysteresis loops, which are incorporated with unique resonant modes. The separation between the resonant fields shows tunable properties with excitation frequencies, thereby offering a wide range of reconfigurable operating parameters. The effective damping parameter has shown a decrement with increasing thickness of the NiFe layers. The effective spin mixing conductance for the NiFe layer was found to be 7.4 ± 0.6 nm−2. The spin-to-charge conversion within these structures has been demonstrated through measurements of the inverse spin Hall effect. Systematic thickness variation revealed that the prominent voltage drop was observed in the NiFe layer compared to the CoFeB layer. Considering the opposite spin Hall angles of Ta and FeMn layer, the direction of the spin flow and spin-to-charge conversion efficiency are summarized. [ABSTRACT FROM AUTHOR]

The influence of Ga on the structural, magnetic and half-metallic properties of Co 2 FeSi 1− x Ga x (0≤ x ≤1) thin films grown on Si (100) substrates using ultra high vacuum magnetron sputtering has been systematically investigated. The linear increase in cubic lattice parameter from 5.63 Å to 5.73 Å and the Curie temperature ( T C ) from 854 K to 941 K with x varying from 0 to 1 indicate the progressive substitution of Ga for Si. The coercivity ( H c ) was found to decrease from 26 Oe ( x =0) to 3 Oe ( x =1) at room temperature and is attributed to the decrease in magnetic anisotropy. The magnetic hysteresis loops measured from 300–873 K revealed that the film where Ga completely replaces Si exhibit better stability in both saturation magnetization ( M s ) and H c with temperature. The increase in coercivity at higher temperatures is attributed to the film to substrate interaction. The measured M s at 100 K decreases from 5.01 µ B /f.u. ( x =0) to 4.49 µ B /f.u. ( x =1) and follows the trend of Slater-Pauling rule. The indirect evidence of half-metallic nature is examined from the temperature dependent electrical resistivity measurements. [ABSTRACT FROM AUTHOR]

• Anomalous saw-tooth and curved Néel domains in the Si/SiO 2 /IrMn/Fe 2 CoSi/Ta bilayers. • Saw-tooth domains attributed to higher magnetic charge density at the domain boundary induced by the IrMn layer. • Curvature for the Néel domain walls attributed to Dzyaloshinskii-Morya interaction (DMI). We report on the evidenced anomalous saw-tooth and curved domains in the Si/SiO 2 /IrMn/Fe 2 CoSi/Ta bilayers. The existence of saw-tooth domains is attributed to higher magnetic charge density at the domain boundary induced by the IrMn layer, while curved domains are apparent due to Dzyaloshinskii-Morya interaction (DMI). On the other hand, straight domain walls are apparent as a result of uni–axial anisotropy and four-fold anisotropy along the easy axis. The curvature for the domain walls decreases upon changing the angle between sample edge and the magnetic field. We believe that the present results would indeed be helpful for the development of the domain wall motion devices. [ABSTRACT FROM AUTHOR]

The effect of film thickness on structure, microstructure, residual stress and soft magnetic properties of Fe 65 Co 35 thin films deposited on Si(001) and MgO(001) substrates was investigated by varying film thickness from 30 to 600 nm. X-ray diffraction studies showed that the FeCo films are polycrystalline in the as-deposited condition irrespective of deposition on Si or MgO substrate. The microstructure of films consisted of spherical grains for 30 nm film thickness and columnar grains for all other film thicknesses. The grain size for the films was found to increase from 15 to 50 nm with increasing film thickness. The sputtered films also exhibited tensile residual stresses with the magnitude of stress decreasing with increasing film thickness. The Fe 65 Co 35 films deposited on both substrates also exhibited very good in-plane soft magnetic properties with a saturation magnetization 4 πM s of ~23.6–23.8 kG and coercivity of ~27–30 Oe without any under-layer only for films with thickness of 30 nm. For all other thicknesses, these films exhibited a significantly higher coercivity. The observed variations in soft magnetic properties with film thickness were explained in terms of residual stress and microstructure of the films. [ABSTRACT FROM AUTHOR]

Abstract: The residual stress instituted in Ni–Mn–Ga thin films during deposition is a key parameter influencing their shape memory applications by affecting its structural and magnetic properties. A series of Ni–Mn–Ga thin films were prepared by dc magnetron sputtering on Si(100) and glass substrates at four different sputtering powers of 25, 45, 75 and 100W for systematic investigation of the residual stress and its effect on structure and magnetic properties. The residual stresses in thin films were characterized by a laser scanning technique. The as-deposited films were annealed at 600°C for 1h in vacuum for structural and magnetic ordering. The compressive stresses observed in as-deposited films transformed into tensile stresses upon annealing. The annealed films were found to be crystalline and possess mixed phases of both austenite and martensite, exhibiting good soft magnetic properties. It was found that the increase of sputtering power induced coarsening in thin films. Typical saturation magnetization and coercivity values were found to be 330emu/cm3 and 215Oe, respectively. The films deposited at 75 and 100W display both structural and magnetic transitions above room temperature. [Copyright &y& Elsevier]

Abstract: The effect of Si/Ge ratio on resistivity and thermopower behavior has been investigated in the magnetocaloric ferromagnetic Gd5Si x Ge4−x compounds with x=1.7–2.3. Microstructural studies reveal the presence of Gd5(Si,Ge)4-matrix phase (5:4-type) along with traces of secondary phases (5:5 or 5:3-type). The x=1.7 and 2.0 samples display the presence of a first order structural transition from orthorhombic to monoclinic phase followed by a magnetic transition of the monoclinic phase. The alloys with x=2.2 and 2.3 display only magnetic transitions of the orthorhombic phase. A low temperature feature apparent in the AC susceptibility and resistivity data below 100K reflects an antiferromagnetic transition of secondary phase(s) present in these compounds. The resistivity behavior study correlates with microstructural studies. A large change in thermopower of −8μV/K was obtained at the magneto-structural transition for the x=2 compound. [Copyright &y& Elsevier]

Abstract: The influence of Fe additions on the martensitic transformation and magnetic properties of Mn-rich Ni–Mn–Ga alloys was investigated by substituting either 1at% Fe for each atomic species or by substituting Ni with varying amounts of Fe. The magnetic structure of the alloys was studied using 57Fe Mössbauer spectroscopy. Mössbauer spectra revealed typical paramagnetic features in Mn-rich Ni–Mn–Ga–Fe alloys owing to the preferential site occupancy of Fe atoms at Ni sites. The evolution of the magnetic properties and phase stability has been correlated with the chemical and atomic ordering in these alloys. [ABSTRACT FROM AUTHOR]

Abstract: Effect of Fe-substitution on the phase formation, partitioning behaviour of Fe in the co-existing phases, magneto-structural transition, magnetic entropy change and associated hysteresis losses has been investigated in Gd5Si2Ge2 alloy. The virgin alloy crystallizes in monoclinic Gd5Si2Ge2-type phase, while Fe-substituted alloys form mixed monoclinic Gd5Si2Ge2-type and orthorhombic Gd5Si4-type phases. Electron probe microanalysis reveals that Fe does not dissolve in the matrix, but influences the magneto-structural transitions. Magneto-structural characterization of the Fe-containing alloys reveals that the Fe-substitution suppresses the structural transition observed at 273K in virgin alloy. A maximum magnetic entropy change, ΔS M of 6.5J/kg-K at 273K was observed for a field change of 2T in Gd5Si2Ge2 alloy. The Fe-substituted alloys exhibit lower value of ΔS M but with reduced hysteresis losses. [Copyright &y& Elsevier]

Abstract: Evolution of structure and magnetocaloric properties in ball-milled Gd5Si2Ge2 and Gd5Si2Ge2/0.1wt% Fe nanostructured powders were investigated. The high-energy ball-milled powders were composed of very fine grains (70–80nm). Magnetization decreased with milling time due to decrease in the grain size and randomization of the magnetic moments at the surface. The magnetic entropy change (ΔS M) was calculated from the isothermal magnetization curves and a maximum value of 0.45J/kgK was obtained for 32h milled Gd5Si2Ge2 alloy powder for a magnetic field change of 2T while it was still low in Fe-contained alloy powders. The thermo-magnetic measurements revealed that the milled powders display distribution of magnetic transitions, which is desirable for practical magnetic refrigerant to cover a wide temperature span. [Copyright &y& Elsevier]

• Thickness dependent domain wall motion in Fe2CoSi. • L – MOKE infers ripple kind of domains for higher thickness films. • Polar plot infers a 4-fold anisotropy in all Fe2CoSi films with different thickness. • Micromagnetic simulations infer void size plays major role for coercivity. We report on the effect of thickness on the magnetic properties and domain wall motion in as deposited Fe 2 CoSi thin films. Reflections present in selected area electron diffraction (SAED) micrograph infer that they are allowed reflections and are related to the Fe 2 CoSi. The coercivity is found to increase with the film thickness and the same is explained on the basis of Néel domain wall model. Longitudinal magneto-optical Kerr effect (L – MOKE) infers that the formation of ripple kind of domains that depend on the orientation of the field. L – MOKE data also infers nearly perfect 4-fold anisotropy for the film with thickness 5 nm and a weaker 4-fold anisotropy at higher thicknesses. Up on varying the angle between magnetic field and the film edge to 0° or 90°, indeed there is a transformation of the film magnetization from easy direction to hard direction. Fast Fourier transform of magnetic force microscopy (MFM) and polar plots infer a uniaxial anisotropy and a four-fold anisotropy in the films. Micromagnetic simulations infer that the coercivity value depends on the void size and enhances up to certain radius, above which it decreases. Present results would indeed be helpful for the future spintronic applications. [ABSTRACT FROM AUTHOR]

• The influence of boron in Co 2 FeSi 1−x B x (x = 0–0.5) Heusler alloys was systematically investigated. • The x-ray diffraction and microstructural analysis confirmed the presence of second phase. • The melting point decreases with increasing boron and merges with ordering temperature at x = 0.5. • The observed compositional shift with boron content is attributed to the formation of second phase. The influence of partial substitution of boron on the structural, microstructure, magnetic and calorimetric properties of Co 2 FeSi 1−x B x (x = 0–0.5) alloys was systematically investigated. The x-ray powder diffraction and microstructural analysis confirmed the presence of second phase in the alloys. From calorimetric studies, it was observed that L2 1 –B2 ordering temperature remain constant whereas the melting point decreases with increasing boron content and merges with ordering temperature at x = 0.5. The Curie temperature (T C) for the alloys x ≥ 0.25 has shown a linear increase with boron concentration. The saturation magnetic moment exhibits a linear decrease and confirms the substitutional effect of boron for Si. With increase in boron content, a compositional shift has been observed which may be attributed to the formation of second phase at the grain boundaries. [ABSTRACT FROM AUTHOR]

• Growth rate and substrate temperature was found to influence the magnetic properties of Fe-Co-Al thin films. • A strong correlation between structure – magnetic - magneto-microstructural properties has been established in Fe-Co-Al thin films. This work reports the effect of growth rate and substrate temperature on the structural, magnetic and magneto-microstructural properties of Fe-Co-Al alloy thin films. 75 nm thick Fe-Co-Al films were deposited on Si 〈1 0 0〉 substrates at room temperature by high power impulse magnetron sputtering at different growth rates viz., 0.67–1.6 Å/s. All the films exhibited a uniform composition of about Fe 60 Co 25 Al 15 irrespective of growth rates. In addition to this, all the films crystallized in single phase with bcc type structure. Growth rate was found to have a considerable impact on the magnetic properties of Fe-Co-Al thin films. Film grown at 1.3 Å/s exhibited an in-plane magnetic anisotropy with large saturation magnetization combined with low coercivity when compared with other films. To improve the magnetic properties further, Fe-Co-Al films were also processed at different substrate temperatures (Ts) viz., 300, 400 and 500 °C. Substrate temperature of about 300 °C was found to have beneficial effect on the soft magnetic characteristics of Fe-Co-Al films. While the crystal structure did not show any perceptible change with processing conditions, magnetic microstructures traced from magneto optic Kerr microscopy displayed substantial change. Upon increase in substrate temperature, during magnetization reversal process, magnetic domain images traced along the easy magnetization direction magnetization showed transformation from branched band domains (as-deposited) → wide band domains (Ts = 300 °C) → less periodic branched band domains (Ts = 400 °C) → ripple domains (Ts = 500 °C). Attempts were made to correlate the achieved magnetic properties in Fe-Co-Al with magnetic microstructures. [ABSTRACT FROM AUTHOR]

Perpendicular Magnetic Anisotropy (PMA) was realized in as-deposited Mo(10)/Co 2 FeAl 0.5 Si 0.5 (CFAS)(3)/MgO(0.5)/Mo multilayer stacks with large perpendicular magnetic anisotropy energy (K eff ). PMA of this multilayer is found to be strongly dependent on the thickness of the individual CFAS (t CFAS ), Mo (t Mo ) and MgO (t MgO ) layers and annealing temperatures. The interactions at the Mo/CFAS/MgO interfaces are critical to induce PMA and are tuned by the interfacial oxidation. The major contribution to PMA is due to iron oxide at the CFAS/MgO interface. X-ray diffraction (XRD) and infrared spectroscopic (FT-IR) studies further ascertain this. However, an adequate oxidation of MgO and the formation of (0 2 4) and (0 1 8) planes of α-Fe 2 O 3 at the optimal Mo buffer layer thickness is mainly inducing PMA in Mo/CFAS/MgO/Mo stack. Microstructural changes in the films are observed by atomic force microscopy (AFM). X-ray photoelectron spectroscopy (XPS) demonstrates the oxidation of CFAS/MgO interface and the formation of Fe–O bonds confirming that the real origin of PMA in Mo/CFAS/MgO is due to hybridization of Fe (3d z 2 ) and O (2p z ) orbitals and the resulted spin-orbit interaction at their interface. The half-metallic nature CFAS with Mo layer exhibiting PMA can be a potential candidate as p-MTJs electrodes for the new generation spintronic devices. [ABSTRACT FROM AUTHOR]

• Higher Growth rates combined with processing temperatures has been found to be effective in improving the soft magnetic properties of FeCoNi thin films. • Presence of magnetic anisotropy in FeCoNi films has been studied through magnetization and magnetic domain imaging studies. • A structure-process-property correlation has been made in FeCoNi films. This paper reports the effect of growth rate and substrate temperature on the composition, structure, microstructure, magnetic and magnetic microstructural properties of Fe-Co-Ni alloy thin films. 200 nm thick Fe-Co-Ni thin films were grown by high power impulse magnetron sputtering on Si 〈1 0 0〉 at different growth rates (viz., 1 – 2.4 Å/s). Films were also thermally processed by modifying the substrate temperatures. Room temperature deposited films showed the presence of FCC structure for all the films. However, films grown at higher substrate temperatures displayed presence of BCC phase co-existing with FCC phase. High saturation magnetization combined with low coercivity has been obtained for the Fe-Co-Ni films grown at higher growth rate and enhanced substrate temperature. Magnetization and magnetic microstructural studies using Kerr microscopy showed anisotropic magnetic properties along the plane of the film with the magnetization reversal dominated by domain wall motion and domain wall rotation. [ABSTRACT FROM AUTHOR]

The effect of substrate and post-annealing temperatures on the structure, microstructure, residual stresses and soft magnetic properties of Fe 70 Co 30 thin films was systematically investigated. Microstructural studies reveal that the films are continuous and undergo changes in shape of grain from plate like to spherical resulting in an increase in grain size with the increase in substrate temperature, whereas the post-annealed films show small pores and no significant grain growth till 500 °C. Coercivity ( H c ) was found decreasing with both the substrate and post-annealing temperatures; however, the best H c value of 26 Oe was obtained for the films deposited at substrate temperature of 500 °C. The post-annealed films exhibited relatively higher H c values. A good combination of high saturation magnetization 4πM s of ~23.2 kG and low coercivity H c of 26–65 Oe was obtained for the films deposited at substrate temperature of 450–500 °C. Residual stress analysis on films with different substrate temperatures shows the presence of tensile stress. The decrease in tensile stress is attributed to the relaxation of thermal stresses in the films. [ABSTRACT FROM AUTHOR]

• Evidence for the vortex state in the Fe 2 CoGe thin films. • Contour graph of FORC infers the formation of vortex state. • Vortex state ∼1 μm with in – plane curling of the magnetization using MFM phase analysis. • Realization of vortex state using MOKE and OOMMF simulations. We report on the evidence for the vortex state in the thin films of Fe 2 CoGe through first order reversal curves, magnetic force microscope, longitudinal magneto-optical Kerr effect and micro-magnetic simulations. Phase purity of the films confirmed through X-ray diffraction, which confirms the A2 type disorder Heusler alloy structure. Contour graph of first order reversal curves infers the formation of vortex state that is useful to understand magnetization reversal and switching process. We do observe the vortex state ∼1 μm with in – plane curling of the magnetization using magnetic force microscope phase analysis. We believe that realization of vortex state formation in Fe 2 CoGe thin films may cater applications in future magnetic data storage and microwave oscillators. [ABSTRACT FROM AUTHOR]

The magnetic ground state, electronic, and elastic properties of Co 2 TaX (X = Al, Ga) are investigated using Density functional theory calculations. The compounds are found to possess mechanical and dynamical stability. Both the compounds exhibit nodal line features in the majority spin channel without the inclusion of spin-orbit coupling (SOC) and become gapped lines when SOC is added. The anomalous Hall effect and anomalous Nernst effect caused by Berry curvature are investigated. Within the region of ± 300 m e V around Fermi level, the maximum values of anomalous Hall conductivities (AHC) are −602.8 S / cm and −593.8 S / cm , while anomalous Nernst conductivities (ANC) are -4.989 Am − 1 K − 1 and 4.934 Am − 1 K − 1 respectively, for Co 2 TaX (X = Al, Ga) compounds. Through the Heisenberg magnetic exchange interactions, the Curie temperatures (T C) for both Co 2 TaX (X = Al, Ga) compounds are calculated to be 560.7 K and 556.3 K within the mean-field approximation (MFA). The magneto-optical response is also examined, and the polar Kerr rotation angles for Co 2 TaAl and Co 2 TaGa at normal incidence were determined to be 0.11 ° and 1.35 ° , respectively. As a result, this study may pave the way for precise property engineering in real-world applications. • The compounds Co 2 TaX (X = Al, Ga) are found to be mechanically and dynamically stable. Both the compounds have nodal line characteristics in the majority spin channel without the inclusion of spin-orbit coupling, and when SOC is added, they become gapped lines. • The intrinsic anomalous Hall and Nernst conductivities are investigated around the Fermi level. • The Curie temperature (T C) is estimated through the Heisenberg magnetic exchange interactions within the mean-field approximation. • Additionally, the magneto-optical response for polar Kerr rotation angle at normal incidence is studied. [ABSTRACT FROM AUTHOR]

Abstract: Melt spun Ni50−x Mn37+x In13 (2≤x≤5) ribbons were investigated for the structure, microstructure, magneto-structural transitions and inverse magnetocaloric effect (IMCE) associated with the first-order martensitic phase transition. The influence of excess Mn in Ni site (or Ni/Mn content) on the martensite transition and the associated magnetic and magnetocaloric properties are discussed. It was found that with the increase in Mn content, the martensitic transition shifted from 325 to 240K as x is varied from 2 to 4, and the austenite phase was stabilized at room temperature. The x=5 ribbon did not show the martensitic transition. For the x=3 ribbon, the structural and magnetic transitions are close together unlike in the x=4 ribbon in which they are far (∼60K) apart. The zero field cooled and field cooled curves support the presence of exchange bias blocking temperature due to antiferromagnetic interactions in the ribbons. A large change in the magnetization between the martensite and austenite phases was observed for a small variation in the Ni/Mn content, which resulted in large IMCE. A large positive magnetic entropy change (ΔS M) of 32J/kgK at room temperature (∼ 300K) for a field change of 5T with a net refrigeration capacity of 64J/kg was obtained in the Ni47Mn40In13 ribbon. [Copyright &y& Elsevier]

Abstract: The structure, microstructure, magneto-structural transition and magnetocaloric effect have been investigated in series of (Gd5−x Zr x )Si2Ge2 alloys with 0≤x≥0.20. X-ray powder diffraction analysis revealed the presence of orthorhombic structure for Zr containing alloys at room temperature in contrast to the monoclinic structure observed in the parent Gd5Si2Ge2 alloy. The microstructural studies reveal that, low Zr addition (x≤0.1) resulted in low volume fraction of detrimental Gd5Si3-type secondary phase compared to that present in the parent alloy. All the Zr containing alloys have shown the presence of only second order magnetic transition unlike the parent alloy showing both first order structural and second order magnetic transition. A moderate (ΔS) M value of −5.5J/kgK was obtained for the x=0.05 alloy at an enhanced operating temperature of 292K compared to −7.8J/kgK at 274K of the parent alloy for an applied field of 2T. The interesting feature of Zr (x=0.05) containing alloy is the wide operating temperature range of ∼25K than that of ∼10–12K for the parent, which resulted in enhanced net refrigerant capacity of 103J/kg compared to that of 53J/kg for the parent alloy. [Copyright &y& Elsevier]

• Co 2 NbGa is mechanically and dynamically stable both at ambient and at high pressures. • Two kinds of disorders B2 and D0 3 -types are studied to ensure the experimental magnetic moment in Co 2 NbGa within coherent potential approximation(CPA). • The value of anomalous Hall conductivity and anomalous Nernst conductivity at ambient is 214.2 S/cm and −2.53 Am−1K−1 within the range of ± 300 meV around Fermi level respectively. • The Curie temperature (TC) is estimated up to 548.7 K through the Heisenberg magnetic exchange interactions within mean-field approximation. • Half-metal to a metal transition under pressure is evidenced through band structure and Fermi surface topology. The ground state electronic, magnetic and elastic properties of Co 2 NbGa are studied using first-principles calculations. The investigated system is mechanically and dynamically stable which is confirmed through Born mechanical stability criteria and positive phonon modes. Two kinds of disorders B2 and D 0 3 -types are studied to ensure the experimental magnetic moment in Co 2 NbGa within coherent potential approximation(CPA). The intrinsic anomalous Hall effect and anomalous Nernst effect are analysed from the Berry curvature point of view. The values of anomalous Hall conductivity and anomalous Nernst conductivity are 214.2 S/cm and −2.53 Am-1K-1 within the range of ± 300 meV around Fermi level respectively, and the same are comparable with the values of other Heusler alloys. The Curie temperature ( T C ) is estimated up to 548.7 K through the Heisenberg magnetic exchange interactions within mean-field approximation. Half-metal to a metal transition under pressure is evidenced through band structure and Fermi surface topology. Also the magnetic, Heisenberg exchange, elastic properties are probed under pressure. [ABSTRACT FROM AUTHOR]

Abstract: The magnetic properties of Nd4.5Fe77− x Mn x B18.5 (x=0, 1 and 2) nanocomposites prepared by the crystallization of amorphous precursors were investigated. Addition of Mn is found to decrease the crystallization temperature of the amorphous ribbons. The intrinsic coercivity i H c and maximum energy product (BH)max increase from 2.6kOe and 9.1MGOe for x=0 to 3.1kOe and 10.3MGOe for x=1, respectively, and the remanence ratio M r/M s increases from 0.70 to 0.72. The effect of Mn on Curie temperature T C and the thermal stability of M r and i H c were also studied. 57Fe Mössbauer spectra have been recorded for x=0, 1 and 2 ribbons at room temperature and site preference of the Mn atoms in Fe3B and Nd2Fe14B phases is discussed using the Mössbauer spectroscopy. [Copyright &y& Elsevier]

Abstract: SmCo5+x wt% Fe (, 5 and 10) nanocomposite powders were synthesized by mechanical milling and were consolidated into bulk shape by spark plasma sintering (SPS) technique. The evolution of structure and magnetic properties were systematically investigated in milled powders as well as in SPS samples. A maximum coercivity of 8.9kOe was achieved in spark plasma sintered SmCo5+5wt% Fe sample. The exchange spring interaction between the hard and soft magnetic phases was evaluated using δM–H measurements and the analysis revealed that the SPS sample containing 5wt% Fe had a stronger exchange coupling between the magnetic phases than that of the sample with10wt% Fe. [Copyright &y& Elsevier]

Highlights • Discovery of electron-diffuson scattering contribution to anomalous Hall effect (AHE). • Only in disordered ferromagnets (FMs) does the weak localization contribute to AHE. • Electron-electron interaction effects do not contribute to AHE in crystalline FMs. • A universal scaling holds between AHE and temperature-dependent part of resistivity. Abstract An exhaustive study of the influence of disorder on anomalous Hall (AH) resistivity ( ρ xy AH ), longitudinal resistivity ( ρ xx ), magnetoresistance and magnetization of Co 2 FeSi (CFS) Heusler alloy thin films of fixed (50 nm) thickness, deposited on Si (1 1 1) substrate, reveals the following. Regardless of the degree of disorder present, the side-jump mechanism gives a dominant contribution to ρ xy AH . A new and novel contribution to both ρ xx and ρ xy AH , characterized by the logarithmic temperature (- lnT) dependence at temperatures below the minimum (T < T min ), exclusive to the amorphous CFS films, originates from the scattering of conduction electrons from the diffusive hydrodynamic modes associated with the longitudinal component of magnetization, called 'diffusons'. The electron-diffuson, e - d , scattering and weak localization (WL) mechanisms compete with the inelastic electron-magnon, e - m , scattering to produce the minimum in ρ xx (T) , whereas the minimum in ρ xy AH (T) is caused by the competing contributions from the e - d and e - m scattering, as WL does not contribute to ρ xy AH . Another novel finding is that the e - d scattering contributions to ρ xy AH (T) and ρ xx (T) scale with each other. In sharp contrast, in crystalline films, enhanced electron-electron Coulomb interaction (EEI), which is basically responsible for the resistivity minimum, does not contribute to ρ xy AH with the result that no minimum in ρ xy AH (T) is observed. The conventional ρ xy AH = f (ρ xx) scaling breaks down completely in the present case. However, when ρ xy AH (T) is corrected for the e - d contribution and ρ xx (T) for both e - d and WL contributions (only EEI) in the amorphous (crystalline) films, the AH coefficient, R A (T) = ρ xy AH (T) / 4 π M s (T) , (calculated from the corrected ρ xy AH and spontaneous magnetization, M s ), perfectly scales with ρ xxT , the temperature-dependent part of the corrected ρ xx , for all the CFS thin films. [ABSTRACT FROM AUTHOR]

• A process developed: Nanocrystalline FeSiBNbCu alloy using commercial grade master alloys. • Flux-shielded air induction melting process purifies the alloy by preventing oxidation and removing impurities. • Impurities present in the commercial grade alloy does not affect the glass forming ability. • Commercial grade alloy: Amorphous phase T C was found to decrease due to the impurities present. • The soft magnetic properties remain almost same for both alloys prepared using pure elements and commercial grade alloys. In the present study, we report a cost-effective method of flux-shielded air induction melting using commercial grade master alloys to produce nanocrystalline soft magnetic Fe 73.5 Si 13.5 B 9 Nb 3 Cu 1 alloy. For comparison, the alloy was made from highly pure raw materials as well. The structure and soft magnetic properties of the commercial grade alloy is similar to the pure one. Air induction melting process with flux not only removed impurities through chemical reactions, it also provided protection from oxidation. Studies of glass formation through experimental findings and Glass Forming Ability (GFA) calculations through ΔT value, α-parameter and P HSS parameter and studies using Calphad (Calculation of Phase Diagram) method have shown that the impurities present in the commercial grade alloy did not affect the glass formation compared to the pure grade alloy. Impurities present in the commercial grade alloy increase the activation energy of crystallization of Fe 3 Si phase, which in turn influences the volume fraction and grain size of Fe 3 Si phase during annealing treatment. Amorphous phase T C was found to decrease due to the impurities present in the amorphous phase and this decreased exchange interaction between Fe-Fe atoms. Saturation magnetization and coercivity of commercial grade alloy are almost equivalent to the alloys prepared with pure elements and they are independent of type and concentration of impurities. Lowest coercivity in commercial grade alloy can be achieved in less annealing time which can lead to increase the productivity and reduce the cost further. [ABSTRACT FROM AUTHOR]

In this work, we have investigated structural, transport, magnetic, magnetocaloric (MC) properties and critical exponents analysis of the (Ni 2.1− x Co x )Mn 0.9 Ga ( x = 0, 0.04, 0.12 and 0.2) Heusler alloys. For all compositions, cubic austenite (A) phase with metallic character is observed at room temperature (RT). With increasing of Co content, magnitude of resistivity decreases, whereas residual resistivity ( ρ 0 ) and electron scattering factor ( A ) increases linearly. Magnetic measurements exhibit that ferromagnetic (FM) Curie temperature ( T C A ) increases towards RT by increasing Co concentration. All samples show conventional MC and maximum magnetic entropy change (Δ S M peak ) of −2.8 Jkg −1 K −1 is observed for x = 0.12 at 147 K under 5 T. Further, hysteresis is observed between cooling and warming cycles around FM-PM ( T C A ) transition in x = 0, 0.04 samples, which suggests that first order nature of transition. However, there is no hysteresis across T C A for x = 0.12 and 0.2 samples suggesting second-order nature of the transition. The critical exponents are calculated for x = 0.12 sample around T C A using Arrott plot and Kouvel-Fisher method, the estimated critical exponents are found closer to the mean-field model reveals the long range ferromagnetic ordering in this composition. [ABSTRACT FROM AUTHOR]

Nanocrystalline spinel ferrite of composition Cu 0.2 Ni 0.2 Mg 0.2 Ca 0.4 Fe 2 O 4 is synthesized by wet hydroxyl co-precipitation method in ethylene glycol as chelating agent and sodium hydroxide as precipitator at pH 8. Ethylene glycol is utilized as the medium which serves as the dissolvable and in addition a complexing specialist. The synthesized particles are annealed at various temperatures. Thermogravimetric investigation affirms that at 280 °C ethylene glycol is dissipated totally and stable phase arrangement happens over 680 °C. FTIR spectra of as synthesized and annealed at 1050 °C recorded between 400 cm −1 and 4000 cm −1 . Structural characterizations of all the samples are carried out by X-ray diffraction (XRD) technique. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) affirm that the particles are spherical and cubic shape with the crystallite size of 12 nm to 32 nm. Magnetic measurements are performed utilizing vibrating sample magnetometer at room temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • TS500 CFAS film has the highest B2 structural order and lowest residual resistivity. • Diffuson and WL effects (e-m and e-p scattering) dominate for T < T min (T > T min) • Phonon-induced non-spin-flip two-band (s↑↓- d↑↓) scattering accounts for. ρ e - p • Thermal renormalization of spin-wave stiffness significantly contributes to. ρ e - m (T) • Suppression of WL an d e – m scattering by magnetic field results in negative MR. An exhaustive study of the effect of anti-site disorder on the 'zero-field', ρ(T , H = 0), and 'in-field', ρ(T , H = 80 kOe), electrical resistivity in 50 nm thick Co 2 FeAl 0.5 Si 0.5 (CFAS) Heusler alloy thin films (deposited on the Si(1 0 0) or SiO 2 /Si(1 0 0) substrates at fixed substrate temperatures in the range 27 ° C ≤ T S ≤ 550 ° C), has been carried out. Irrespective of the strength of disorder, resistivity goes through a minimum as a function of temperature at T = T min. With increasing substrate temperature, the crystalline order of the CFAS thin films improves so much so that the films deposited at 500 °C have the lowest anti-site disorder within the B2 structure and the least residual resistivity. A quantitative comparison of our results with the predictions of the existing theoretical models permits us to unambiguously identify the diffusive and ballistic transport mechanisms, responsible for ρ(T , H = 0) and ρ(T , H = 80 kOe) in different temperature ranges and accurately determine their relative magnitudes. The electron-diffuson (e – d) scattering and weak localization (WL) mechanisms, responsible for negative temperature coefficient of resistivity (TCR) for T < T min , compete with the positive TCR mechanisms, electron-magnon (e – m) and electron–phonon (e – p) scattering, to produce the resistivity minimum at T min. The e – d and WL contributions to ρ, ρ e - d and ρ wl , dominate over the e – m and e – p contributions, ρ e - m and ρ e - p , for T < T min whereas the reverse is true for T > T min . At any given temperature, ρ e - d , ρ wl and ρ e - m decrease while ρ e - p increases as the atomic order improves with increasing substrate temperature, T S. ρ e - p and ρ e - m originate from the phonon-induced non-spin-flip two-band (s↑↓- d↑↓) scattering and magnon - induced spin-flip s - d interband (s↑↓- d↓↑) transitions, respectively. In all the CFAS films, except for the one deposited at T S = 27 ° C , the thermal renormalization of the spin-wave stiffness, due to the electron - magnon interaction, contributes significantly to ρ e - m (T). Furthermore, we demonstrate that the negative magnetoresistance (MR) is a consequence of a progressive suppression of the WL effect and e – m scattering by external magnetic field. However, the WL contribution to MR turns out to be negligibly small as the e – m contribution almost entirely accounts for MR over the temperature range 5 K ≤ T ≤ 300 K. [ABSTRACT FROM AUTHOR]

Highlights • The substitution of Fe in Ni 47 Mn 40 In 13 enhances the Curie temperature of martensitic phase. The martensitic transition shifts to low temperature with the increase of Fe concentration. • The present study reveals the enhancement of magnetic entropy change in Fe doped Ni-Mn-In alloy. • The huge increase of ΔS M value in Ni 47 Mn 40- x Fe x In 13 (x = 2) alloy at room temperature is expected to have an application in the modern magnetic refrigeration technology. Abstract We report the effect of Fe on the martensitic transitions in Ni 47 Mn 40- x Fe x In 13 (x = 1 and 2) alloys and associated magnetocaloric effect. Structural and magnetic transitions are observed in x = 1 and 2 alloys. The martensitic transition shifts to low temperature with the increase of Fe concentration. The maximum positive entropy change (ΔS M) with quite large magnitude of 22 Jkg−1K−1 (x = 1) and 51.2 Jkg-1K-1 (x = 2) are observed for a field change of 50 kOe. Substitution of Fe enhances the magnetization as well as increases the ΔS M more than a twice in the x = 2 system. [ABSTRACT FROM AUTHOR]

• Observation of resonances corresponding to different standing spin-wave modes. • IP magnetocrystalline anisotropy decreases with increasing crystalline order. • The TS500 CFTS thin film has values of M S and α , conducive for spintronics. • The OP anisotropy field H k ⊥ is an order of magnitude higher than in-plane. H k ‖ • In OP, LLG damping, Δ H θ H are responsible for the dip near θ H = 0 in Δ H (θ H) plots. • TMS contribution to Δ H is appreciable only in the range 70 ° ≤ θ H ≤ 11. 0 ° 100 nm Co 2 Fe 0.5 Ti 0.5 Si (CFTS) thin films were grown on Si (1 0 0) substrate at different substrate temperatures T S to study the effect of site disorder on the magnetization relaxation processes and magnetic anisotropy in them. To this end, two different ferromagnetic resonance (FMR) techniques have been employed: broad-band (3 – 17 GHz) FMR at a fixed static magnetic field angle in the 'in-plane' (IP) sample geometry, and X-band (9.45 GHz) FMR at different polar field-angles, θ H , in the 'out-of-plane' (OP) sample configuration. Increase in T S reduces the degree of disorder and improves crystalline order. Improvement in crystallinity, in turn, results in the decrease in the strength of magnetocrystalline anisotropy. Irrespective of the degree of disorder present, the OP anisotropy field, H k ⊥ , is an order of magnitude higher than the IP counterpart, H k ‖. Out of the CFTS thin films studied, the film (TS500), deposited at T S = 500 °C, has the maximum L2 1 crystalline order, maximum saturation magnetization (M S = 779 G), and the least values for H k ‖ (5.3 Oe), H k ⊥ (17 Oe), Landé splitting factor, g = 2.02 , and the Gilbert damping constant, α = 5.5 × 10 - 3 . These optimum values of M S , g and α , at room temperature, are conducive for spintronics applications. In the OP configuration, the FMR linewidth, Δ H ⊥ , mainly arises from the intrinsic Landau-Lifshitz-Gilbert damping and extrinsic angular spread of crystallite misorientation. However, the extrinsic two-magnon scattering contribution to Δ H ⊥ , is appreciable only in the angular range 70 ° ≤ θ H ≤ 110 ° . [ABSTRACT FROM AUTHOR]

Abstract: The structural, magnetic, magnetocaloric and magnetotransport properties of Ni46Co4Mn38Sb12 melt spun ribbons have been systematically investigated. The partially ordered B2 phase of the as-spun ribbon transforms to fully ordered L21 phase upon annealing, which signifies a considerable change of the atomic ordering in the system. The presence of atomic disorder in the as-spun ribbon gives rise to a higher martensitic transition temperature and a lower magnetization as compared to the bulk sample. However, annealing the ribbons helps in regaining the bulk properties to a large extent. Significant changes in magnetocaloric effect, exchange bias and magnetoresistance have been observed between the as-spun and the annealed ribbons, indicating the role of atomic ordering on the functional as well as fundamental properties in the Heusler system. Importantly, the study shows that one can reduce the hysteresis loss by preparing melt spun alloys and subjecting them to appropriate annealing conditions, which enable them to become practical magnetic refrigerants. [Copyright &y& Elsevier]

Abstract: Small crystallites of a metastable phase Co0.5Pt0.5 are precipitated by heating a rheological liquid precursor of cobalt–hydrazine complex and platinum chloride H2PtCl6·xH2O in polymer molecules of poly(vinylpyrrolidone) (PVP) in ethylene glycol. The hydrazine co-reduces nascent atoms from the Co2+ and Pt4+ that recombine and grow as Co0.5Pt0.5. The PVP molecules cap a growing Co0.5Pt0.5 as it achieves a critical size so that it stops growing further in given conditions. X-ray diffraction pattern of a recovered powder reveals a crystalline Co0.5Pt0.5 phase (average crystallite size D∼8nm) of a well-known Fm3m-fcc crystal structure with the lattice parameter a=0.3916nm (density ρ=14.09g/cm3). A more ordered L10 phase (ρ=15.91g/cm3) transforms (D≥25nm) upon annealing the powder at temperature lesser than 700°C (in vacuum). At room temperature, the virgin crystallites bear only a small saturation magnetization M s=5.54emu/g (D=8nm) of a soft magnet and it hardly grows on bigger sizes (D≤31nm) in a canted ferromagnetic structure. A rectangular hysteresis loop is markedly expanded on an optimally annealed L10 phase at 800°C for 60min, showing a surface modified coercivity H c=7.781kOe with remnant ratio M r/M s=0.5564, and M s=39.75emu/g. Crystallites self-assembled in an acicular shape tailor large H c from ideal single domains and high magnetocrystalline anisotropy of a hard magnet L10 phase. [Copyright &y& Elsevier]

Abstract: Alloys of Fe77Ga23B x (x=0, 0.025, 0.050, 0.075 and 0.1) were heat treated at 1000°C/10h and characterized for microstructural features and magnetostriction. The study indicates that the parent alloy consists of three phases viz. A2 as the major phase and L12 and DO3 as minor phases. However, the volume fraction of L12 and DO3 decreases with B addition and as a result magnetostriction improves. The decrease in volume fraction of these phases is attributed to B-segregation to the grain boundary, which seems to prevent the formation of these phases. The alloy with x=0.1, however, exhibits an additional Fe2B phase and consequently its presence leads to the re-emergence of the DO3 phase, affecting the magnetostriction. [Copyright &y& Elsevier]

Abstract: Polycrystalline Ni–Mn–Ga thin films were deposited by the d.c. magnetron sputtering on well-cleaned substrates of Si(100) and glass at a constant sputtering power of 36W. We report the influence of sputtering pressure on the composition, structure and magnetic properties of the sputtered thin films. These films display ferromagnetic behaviour only after annealing at an elevated temperature and a maximum saturation magnetization of 335emu/cc was obtained for the films investigated. Evolution of martensitic microstructure was observed in the annealed thin films with the increase of sputtering pressure. The thermo-magnetic curves exhibited only magnetic transition in the temperature range of 339–374K. The thin film deposited at high sputtering pressure of 0.025mbar was found to be ordered L21 austenitic phase. [Copyright &y& Elsevier]

Abstract: The Fe73.5Cu1Nb3Si13.5B9 FINEMET alloy has been prepared by the rapid solidification technique. The critical behaviour of this alloy in the amorphous as well as in its nanocrystalline states has been studied near their respective Curie temperatures. From the values of the critical exponents one can conclude that the alloy behaves like a 3D Heisenberg ferromagnet in the amorphous and nanocrystalline states. But there exists a slight increase in the value of β for the alloy annealed at 823K (the nanocrystalline state) as observed in most of the amorphous alloys. [Copyright &y& Elsevier]

Structural, magnetic and 57Fe Mössbauer investigations of indium (In) doped cobalt ferrite are reported. Polycrystalline CoFe 2−x In x O 4 , x = 0, 0.2, 0.4, 0.6, 0.8 samples are prepared by sol–gel method. In contrast to most of the literature, in the present work phase pure samples are obtained, except for x = 0.2. The presence of ferrimagnetic ordering in all the samples is confirmed from in-field 57Fe Mössbauer spectroscopy measurements. The cation distribution is obtained unambiguously from the combined analysis of Raman and in-field 57Fe Mössbauer spectroscopy measurements. The variation of magnetic moment values calculated from the obtained cation distribution are found to match qualitatively with the experimental values, supporting the analysis of in-field 57Fe Mössbauer and Raman spectroscopy measurements. [ABSTRACT FROM AUTHOR]