The effect of ball milling on the structural, magnetic and exchange bias properties of Ni50Mn36Fe2Sb12 Heusler alloys was studied. The ball milled samples exhibited coexisting austenite and martensite phases at room temperature, while annealing supresses the austenite phase completely. Ball milling was found to reduce the grain size, which resulted in the weakening of the ferromagnetic properties. An exchange bias field of 111 Oe and coercivity of 826 Oe were observed at 5 K in the as-milled sample, in contrast to the bulk alloy values of 288 Oe and 292 Oe, respectively. Annealing causes an increase in the ferromagnetic ordering and a decrease in the interfacial exchange coupling, resulting in a decrease of both exchange bias and coercivity.
The authors developed a preparation technique of Co_2FeSi full-Heusler alloy films with the L2_1-ordered structure on silicon-on-insulator (SOI) substrates, employing rapid thermal annealing (RTA). The Co_2FeSi full-Heusler alloy films were successfully formed by RTA-induced silicidation reaction between an ultrathin SOI (001) layer and Fe/Co layers deposited on it. The highly (110)-oriented L2_1-phase polycrystalline full-Heusler alloy films were obtained at the RTA temperature of 700 C. Crystallographic and magnetic properties of the RTA-formed full-Heusler alloy films were qualitatively the…
The authors developed a new analysis approach for evaluation of atomic ordering in full-Heusler alloys, which is extension of the commonly used Webster model. Our model can give accurate physical formalism for the degree of atomic ordering in the L21 structure, including correction with respect to the fully disordered A2 structure, i.e., the model can directly evaluate the degree of L21-ordering under a lower ordering structure than the complete B2-ordering structure. The proposed model was applied to full-Heusler Co2FeSi alloy thin films formed by rapid thermal annealing. The film formed at T…
The authors demonstrated that a full-Heusler Co2FeGe (CFG) alloy thin film was epitaxially grown by rapid-thermal-annealing-induced germanidation of an Fe/Co/pseudo-Ge(001)-on-insulator (GOI) multilayer formed on a Si-on-insulator (SOI) substrate. X-ray diffraction (XRD) measurements with the out-of-plane and in-plane configurations revealed that the CFG film was epitaxially grown along the [001] direction with the in-plane epitaxial relation of CFG[100]||GOI[100], although the film slightly contained a texture component. The strong (111) and (200) superlattice diffraction intensities indicate…
The anomalous Hall effect (AHE) in the Heusler compounds Co$_{2}$FeSi and Co$_{2}$FeAl is studied in dependence of the annealing temperature to achieve a general comprehension of its origin. We have demonstrated that the crystal quality affected by annealing processes is a significant control parameter to tune the electrical resistivity $ρ_{xx}$ as well as the anomalous Hall resistivity $ρ_{ahe}$. Analyzing the scaling behavior of $ρ_{ahe}$ in terms of $ρ_{xx}$ points to a temperature-dependent skew scattering as the dominant mechanism in both Heusler compounds.
The (Co,Ni)Al2O4 is an aluminum transition metals oxide which falls into the category of aluminate spinels. The synthesis of nano-crystalline spinels has been investigated extensively due to their potential applications such as a high-density magnetic recording, microwave devices magnetic fluids, ceramic pigment as well as a heterogeneous catalytic material. In the present study, attempts have been made to synthesise the nano-crystalline (Co,Ni)Al2O4 spinel powders by ball milling and subsequent annealing. An alloy of Al70 Ni15 Co15, exhibiting the formation of a complex intermetallic compound…
In the present study, low-temperature synthesis of (Cu Fe)Al2O4 and (Cu Cr Fe)Al2O4 spinels from the quasicrystalline phases was investigated with the variation of process parameters during milling and annealing. The milling of the quasicrystalline materials was carried out in an attritor mill at 400 rpm for 40 hours with ball to powder ratio of 40:1 in hexane medium. Subsequently, annealing was performed in an air ambience for 10, 20, and 40 h at 400, 500, 600 and 700 C in side a furnace in order to oxidize the mechanically milled quasicrystalline phase for the possible formation of the spine…
We report on the influence of the improved L21 ordering degree on the magnetic properties of Co2MnSi Heusler films. Different fractions of the L21 phase are obtained by different post-growth annealing temperatures ranging from 350 degC to 500 degC. Room temperature magneto-optical Kerr effect measurements reveal an increase of the coercivity at an intermediate annealing temperature of 425 degC, which is a fingerprint of an increased number of pinning centers at this temperature. Furthermore, Brillouin light scattering studies show that the improvement of the L21 order in the Co2MnSi films is c…
We have systemically studied the effects of annealing temperature and alloy composition on the structural and magnetic properties of bulk Ni$_{2}$MnGe and Ni$_{2.1}$Mn$_{0.9}$Ge Heusler alloys. We have observed that both annealing temperature and the alloy composition drastically alter the phases found in the samples due to the presence of competing ternary phases. Annealing at 900 and 950 $^{\circ}$C for both alloy compositions facilitate the formation of L2$_{1}$ Heusler phase. Nevertheless, formation of Ni$_{5}$Mn$_{4}$Ge$_{3}$ and Ni$_{16}$Mn$_{6}$Ge$_{7}$ phases cannot be prevented for Ni…
10 nm and 50 nm Co$_{2}$FeAl (CFA) thin films have been deposited on MgO(001) and Si(001) substrates by magnetron sputtering and annealed at different temperatures. X-rays diffraction revealed polycrystalline or epitaxial growth (according to the relation CFA(001)[110]//MgO(001)[100] epitaxial relation), respectively for CFA films grown on a Si and on a MgO substrate. For these later, the chemical order varies from the A2 phase to the B2 phase when increasing the annealing temperature (Ta) while only the A2 disorder type has been observed for CFA grown on Si. Microstrip ferromagnetic resonance…
Mechanical alloying (MA) has been used to fabricate the Co2FeAl Heusler alloy with a nanocrystalline structure. The formation mechanism of the alloy has been investigated. Rietveld analysis showed that all samples that were milled for more than 15 hours had an L21 structure with a space group of Fm3m. The crystallite size and internal strain of the samples were calculated using the Williamson-Hall equation. With mechanical alloying of up to 20 hours the crystallite size of Co2FeAl increased, after which the crystallite size started to decrease. In contrast, internal strain first decreased duri…
Half-Heusler alloys (MgAgSb structure) are promising thermoelectric materials. RNiSn half-Heusler phases (R=Hf, Zr, Ti) are the most studied in view of their thermal stability. The highest dimensionless figure of merit (ZT) obtained is ~1 in the temperature range ~450-900oC, primarily achieved in nanostructured alloys. Through proper annealing, ZT~1.2 has been obtained in a previous ZT~1 n-type (Hf,Zr)NiSn phase without the nanostructure. There is an appreciable increase in the power factor, decrease in charge carrier density, and increase in carrier mobility. The findings are attributed to th…
Science-driven design of future thermoelectric materials requires a deep understanding of the fundamental relationships between microstructure and transport properties. Grain boundaries in polycrystalline materials influence the thermoelectric performance through the scattering of phonons or the trapping of electrons due to space-charge effects. Yet, the current lack of careful investigations on grain boundary-associated features hinders further optimization of properties. Here, we study n-type NbCo1-xPtxSn half-Heusler alloys, which were synthesized by ball milling and spark plasma sintering …
Heusler alloy Co2FeAl was employed as ferromagnetic layers in Co2FeAl/Ru/Co2FeAl synthetic antiferromagnet structures. The experimental results show that the structure with a Ru thickness of 0.45 nm takes on strongly antiferromagnetic coupling, which maintains up to 150 oC annealing for 1 hour. The structure has a very low saturation magnetization Ms of 425 emu/cc, a low switching field Hsw of 4.3 Oe and a high saturation field Hs of 5257 Oe at room temperature, which are favorable for application in ultrahigh density magnetic read heads or other magnetic memory devices. XRD study testifies th…
We present a study of the dynamic magnetic properties of TiN-buffered epitaxial thin films of the Heusler alloy Fe$_{1.5}$CoGe. Thickness series annealed at different temperatures are prepared and the magnetic damping is measured, a lowest value of $α=2.18\times 10^{-3}$ is obtained. The perpendicular magnetic anisotropy properties in Fe$_{1.5}$CoGe/MgO are also characterized. The evolution of the interfacial perpendicular anisotropy constant $K^{\perp}_{\rm S}$ with the annealing temperature is shown and compared with the widely used CoFeB/MgO interface. A large volume contribution to the per…
Heusler compounds form a numerous class of intermetallics, which include two families of compositions ABC and AB2C, usually referred to as half- and full-Heusler compounds, respectively. Given their tunable electronic properties, made possible by adjusting the chemical composition, these materials are currently considered for the possible use in sustainable technologies such as solar energy and thermoelectric conversion. According to theoretical predictions, Sb substitution in the TiFe2Sn full-Heusler compound is thought to yield band structure modifications that should enhance the thermoelect…
This paper shows the correlation between chemical order, lattice strains and magnetic properties of Heusler Co2FeAl films epitaxially grown on MgO(001). A detailed magnetic characterization has been performed using vector field magnetometery combined with numerical Stoner-Wohlfarth analysis. We demonstrate the presence of three types of in-plane anisotropies: one biaxial, as expected for the cubic symmetry, and other two uniaxial ones. The three anisotropies show different behavior with the annealing temperature. The biaxial anisotropy shows a monotonous increase. The uniaxial anisotropy, para…
We report the magnetic properties of mechanically milled Co$_{0.2}$Zn$_{0.8}$Fe$_2$O$_4$ spinel oxide. After 24 hours milling of the bulk sample, the XRD spectra show nanostructure with average particle size $\approx$ 20 nm. The as milled sample shows an enhancement in magnetization and ordering temperature compared to the bulk sample. If the as milled sample is annealed at different temperatures for the same duration, recrystallization process occurs and approaches to the bulk structure on increasing the annealing temperatures. The magnetization of the annealed samples first increases and the…
The authors developed a new analysis technique for atomic disorder structures in full-Heusler alloys using x-ray diffraction (XRD) with Co-Ka and Cu-Ka sources. The developed technique can quantitatively evaluate all the atomic disorders for the exchanges between X, Y, and Z atoms in full-Heusler X2YZ alloys. In particular, the technique can treat the DO3 disorder that cannot be analyzed by ordinary Cu-Ka XRD. By applying this technique to full-Heusler Co2FeSi alloy thin films formed by rapid thermal annealing (RTA), RTA-temperature (TA) dependence of the atomic disorders was revealed. The sit…
Single phase Mn doped (2 at %) ZnO samples have been synthesized by solid-state reaction technique. Before the final sintering at 500 C, the mixed powders have been milled for different milling periods (6, 24, 48 and 96 hours). The grain sizes of the samples are very close to each other (~ 32 \pm 4 nm). However, the defective state of the samples is different from each other as manifested from the variation of magnetic properties and electrical resistivity with milling time. All the samples have been found to be ferromagnetic with clear hysteresis loops at room temperature. The maximum value f…
We report on perpendicular magnetic anisotropy (PMA) in a Pt/Co2FeAl/MgO sandwiched structure with a thick Co2FeAl layer of 2-2.5 nm. The PMA is thermally stable that the anisotropy energy density Ku is 1.3{\times}106 erg/cm3 for the structure with 2 nm Co2FeAl after annealing at 350 oC. The thicknesses of Co2FeAl and MgO layers greatly affect the PMA. Our results provide an effective way to realize relative thick perpendicularly magnetized Heusler alloy films.
We report the current-perpendicular-to-plane giant magnetoresistance of a spin valve with Co2MnSi (CMS) Heusler alloy ferromagnetic electrodes. A multilayer stack of Cr/Ag/Cr/CMS/Cu/CMS/Fe25Co75/Ir28Mn72/Ru was deposited on a MgO (001) single crystal substrate. The bottom CMS layer was epitaxially grown on the Cr/Ag/Cr buffer layers and was ordered to the L21 structure after annealing at 673 K. The upper CMS layer was found to grow epitaxially on the Cu spacer layer despite the large lattice mismatch between Cu and CMS. The highest MR ratios of 8.6% and 30.7% for CPP-GMR were recorded at room …
MgO-barrier magnetic tunnel junctions with half-metallic Heusler alloy electrodes attracted much attentions for spintronics applications. However, a couples of issues related to materials still remain to be resolved for practical uses. Recently, quarterly equiatomic Heusler alloys attracted attentions as advanced Heusler alloys. CoIrMnZ (Z = Al, Si, Ga, and Ge) half-metallic Heusler alloys were designed and predicted to have moderate Curie temperatures and to be a lattice-matched with the MgO barrier, being advantageous to traditional Co2 Heusler alloys [T. Roy et al., J. Magn. Magn. Mater. 49…
Perpendicular magnetic anisotropy (PMA) in ultrathin magnetic structures is a key ingredient for the development of electrically controlled spintronic devices. Due to their relatively large spin-polarization, high Curie temperature and low Gilbert damping the Co-based full Heusler alloys are of special importance from a scientific and applications point of view. Here, we study the mechanisms responsible for the PMA in Pt/Co-based full Heusler alloy/MgO thin films structures. We show that the ultrathin Heusler films exhibit strong PMA even in the absence of magnetic annealing. By means of ferro…
Half-Heusler (HH) phases (space group F43m, Clb) are increasingly gaining attention as promising thermoelectric materials in view of their thermal stability, scalability, and environmental benignity as well as efficient power output. Until recently, the verifiable dimensionless figure of merit (ZT) of HH phases has remained moderate near 1, which limits the power conversion efficiency of these materials. We report herein ZT~1.3 in n-type (Hf,Zr)NiSn alloys near 850 K developed through elemental substitution and simultaneously embedment of nanoparticles in the HH matrix, obtained by annealing t…
In the recent years graphitization of ion-beam induced amorphous layers became the basic tool for device fabrication in diamond. The etchable graphitic layers can be removed to form free-standing membranes into which the desired structures can be sculpted using FIB milling. The optical properties of the devices fabricated using this method are assumed on the model of sharp diamond-air interface. The real quality of this interface could depend on degree of graphitization of the amorphous damage layers after annealing. In the present work the graphitization process was studied using conventional…
This work reports the formation of nano- crystalline Al50Cu28Fe22 by high-energy milling. For obtaining the nano-crystalline material, the Al50Cu28Fe22 alloy synthesized through slow cooling of the molten alloy was subjected to ball milling, which was carried out in attritor mill at 400 rpm for 5 h, 10 h, 20 h, 40 h and 80 h with a ball to powder ratio 40 : 1 in hexane medium. The x-ray diffraction observation of ball-milled samples revealed that the milling duration of $5h$ to $40 hrs$ has led to the formation of nano-phase. The average crystallite size comprising the nano-phase has been foun…
All-Heusler multilayer structures have been investigated by means of high kinetic x-ray photoelectron spectroscopy and x-ray magnetic circular dichroism, aiming to address the amount of disorder and interface diffusion induced by annealing of the multilayer structure. The studied multilayers consist of ferromagnetic Co$_2$MnGe and non-magnetic Rh$_2$CuSn layers with varying thicknesses. We find that diffusion begins already at comparably low temperatures between 200 $^{\circ}$C and 250 $^{\circ}$C, where Mn appears to be most prone to diffusion. We also find evidence for a 4 Å thick magnetical…
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. Significa…
In this study, to obtain perpendicular magnetic tunnel junctions (p-MTJs) using half-metallic ferromagnets (HMFs), several methods were developed to induce perpendicular magnetic anisotropy (PMA) in full-Heusler Co2FeSi (CFS) alloy thin layers in an MTJ multilayer composed of a layered CFS/MgO/CFS structure. Oxygen exposure at 2.0 Pa for 10 min after deposition of the bottom CFS layer was effective for obtaining PMA in the CFS layer. One of the reasons for the PMA is the formation of nearly ideal CFS/MgO interfaces due to oxygen exposure before the deposition of the MgO layer. The annealing pr…
We report the evolution of magnetic moment as well as magnetic anisotropy with crystalline order in Co$_2$MnSi thin films grown on $(100)$ MgO by pulsed laser deposition. The films become more ordered as the annealing temperature ($T_A$) increases from 400 to 600 $^0$C. The extent of \emph{L}$2_1$ ordering in the films annealed at 600 $^0$C is $\approx 96%$. The static magnetization measurements by vibrating sample magnetometry shows a maximum moment of 4.95 $μ_B$ per formula unit with low coercivity ($H_C$ $\approx$ 65 Oe) in the films annealed at 600 $^0$C. A rigorous analysis of the azimuth…
Co2MnAl has been predicted to have Weyl points near Fermi level which is expected to give rise to exotic transverse transport properties such as large anomalous Hall(AHE) and Nernst effects(ANE) due to large Berry curvature. In this study, the effect of Fermi level position and atomic ordering on AHE and ANE in Co2MnAl1-xSix were studied systematically. The Co2MnAl film keeps B2-disordred structure regardless of annealing temperature, which results in much smaller anomalous Hall conductivity sigma_xy and transverse Peltier coefficient sigma_xy than those calculated for L21-ordered Co2MnAl. Our…
We present a detailed experimental study of bulk and powder samples of the Heusler shape memory alloy Ni$_2$MnGa, including zero-field static and dynamic $^{55}$Mn NMR experiments, X-ray powder diffraction and magnetization experiments. The NMR spectra give direct access to the sequence of structural phase transitions in this compound, from the high-T austenitic phase down to the low-T martensitic phase. In addition, a detailed investigation of the so-called rf-enhancement factor provides local information for the magnetic stiffness and restoring fields for each separate coordination, structur…
Previous studies indicated that intrinsic point defects play a crucial role for the density of states of ferromagnetic half-metals in the band gap region: At large concentrations, defect-derived bands might close the gap at the Fermi energy in the minority spin channel. In this work, structural disorder in the Co- and Mn-sublattices of the full Heusler alloy Co_2-xMn_1+xSi (-1 < x < 2) is investigated with a cluster expansion approach, parametrized using all-electron density functional theory calculations. By establishing two separate cluster expansions, one for the formation energy and one fo…
Novel Ni-Co-Mn-Ti all-d-metal Heusler alloys are exciting due to large multicaloric effects combined with enhanced mechanical properties. An optimized heat treatment for a series of these compounds leads to very sharp phase transitions in bulk alloys with isothermal entropy changes of up to 38 J kg$^{-1}$ K$^{-1}$ for a magnetic field change of 2 T. The differences of as-cast and annealed samples are analyzed by investigating microstructure and phase transitions in detail by optical microscopy. We identify different grain structures as well as stoichiometric (in)homogenieties as reasons for di…
Among the large class of Heusler compounds, Co2CrAl is predicted to be 100 % spin polarized and is hence, a potential candidate for application in spintronics. So far, the predicted properties have not been experimentally realized which may be attributed to the phase segregated nature of samples. This phase segregation is avoided using floating zone growth. However, the grown sample was found to have undergone phase transformation via spinodal decomposition at low temperatures. In the present work, thermal annealing has been done on the spinodally decomposed samples and its effect on microstru…
We investigate thickness series of films of the Heusler alloy Co$_2$FeAl in order to study the effect of annealing on the interface with a MgO layer and on the bulk magnetic properties. Our results reveal that while the perpendicular interface anisotropy constant $K^{\perp}_{\rm S}$ is zero for the as-deposited samples, its value increases with annealing up to a value of $1.14\, \pm \,0.07$~mJ/m$^2$ for the series annealed at 320$^{\rm o}$C and of $2.07\, \pm \,0.7$~mJ/m$^2$ for the 450$^{\rm o}$C annealed series owing to a strong modification of the interface during the thermal treatment. Thi…
The thermoelectric properties of n type semiconductor, TiNiSn is optimized by partial substitution with metallic, MnNiSb in the half Heusler structure. Herein, we study the transport properties and intrinsic phase separation in the system. The Ti1-xMnxNiSn1-xSbx alloys were prepared by arc-melting and were annealed at temperatures obtained from differential thermal analysis and differential scanning calorimetry results. The phases were characterized using powder X-ray diffraction patterns, energy dispersive X-ray spectroscopy, and differential scanning calorimetry. After annealing the majority…
We report the evolution of crystallographic structure, magnetic ordering and electronic transport in thin films of full-Heusler alloy Co$_2$MnSi deposited on (001) MgO with annealing temperatures ($T_A$). By increasing the $T_A$ from 300$^\circ$C to 600$^\circ$C, the film goes from a disordered nanocrystalline phase to $B2$ ordered and finally to the $L2_1$ ordered alloy. The saturation magnetic moment improves with structural ordering and approaches the Slater-Pauling value of $\approx 5.0 μ_B$ per formula unit for $T_A$ = 600$^\circ$C. At this stage the films are soft magnets with coercive a…
In the present investigation the pure elemental powder mixture of Al (70 at%) Ni (15 at %), Cu (15 at %) was mechanically milled in an attritor ball mill for 10, 20, 40, 60, 80 and 100 hours in hexane medium at 400 rpm. The isothermal annealing of 100 h mechanically milled powder has been done at 700 0C for 20, 40 and 60 hours. The mechanically alloyed powders are characterized using X-ray diffraction, differential thermal analysis and transmission electron microscopy techniques. It was observed that mechanical alloying led to the formation of nano tau 3 phases in Al70 Cu15Ni15 after 80 h of m…
The structure, magnetic and transport properties of thin films of the Heusler ferrimagnet Mn_{2}CoAl have been investigated for properties related to spin gapless semiconductors. Oriented films were grown by molecular beam epitaxy on GaAs substrates and the structure was found to transform from tetragonal to cubic for increasing annealing temperature. The anomalous Hall resistivity is found to be proportional to the square of the longitudinal resistivity and magnetization expected for a topological Berry curvature origin. A delicate balance of the spin-polarized carrier type when coupled with …
Epitaxial thin films of the theoretically predicted half metal Co2Cr0.6Fe0.4Al were deposited by dc magnetron sputtering on different substrates and buffer layers. The samples were characterized by x-ray and electron beam diffraction (RHEED) demonstrating the B2 order of the Heusler compound with only a small partition of disorder on the Co sites. Magnetic tunneling junctions with Co2Cr0.6Fe0.4Al electrode, AlOx barrier and Co counter electrode were prepared. From the Julliere model a spin polarisation of Co2Cr0.6Fe0.4Al of 54% at T=4K is deduced. The relation between the annealing temperature…
Optomechanical resonators were fabricated on a silicon-on-insulator (SOI) substrate that had been implanted with phosphorus donors. The resonators' mechanical and optical properties were then measured (at 6 kelvin and room temperature) before and after the substrate was annealed. All measured resonators survived the annealing and their mechanical linewidths decreased while their optical and mechanical frequencies increased. This is consistent with crystal lattice damage from the ion implantation causing the optical and mechanical properties to degrade and then subsequently being repaired by th…
The structure and magnetic properties of nanocrystalline PrCo$_3$ prepared by high-energy milling technique have been investigated by means of X-ray diffraction using the Rietveld method coupled to Curie temperature and magnetic measurements. The as-milled samples were subsequently annealed in temperature range from 750 to 1050 °C for 30 min to optimize the extrinsic properties. From x-ray studies of magnetic aligned samples, the magnetic anisotropy of this compounds is found uniaxial. The Curie temperature is 349 °K and no saturation reached at room temperature for applied field of 90 kOe. Th…
Nanocrystalline Al-Mg alloys are used to isolate the effect of grain boundary doping on the strength of nanostructured metals. Mg is added during mechanical milling, followed by low homologous temperature annealing treatments to induce segregation without grain growth. Nanocrystalline Al -7 at.% Mg that is annealed for 1 h at 200 °C is the strongest alloy fabricated, with a hardness of 4.56 GPa or approximately three times that of pure nanocrystalline Al. Micropillar compression experiments indicate a yield strength of 865 MPa and a specific strength of 329 kN m/kg, making this one of the stro…
We have studied the effect of ageing within the miscibility gap on the electric, magnetic and thermodynamic properties of a non-stoichiometric Heusler Cu-Al-Mn shape-memory alloy, which undergoes a martensitic transition from a $bcc$-based ($β$-phase) towards a close-packed structure ($M$-phase). Negative magnetoresistance which shows an almost linear dependence on the square of magnetization with different slopes in the $M$- and $β$-phases, was observed. This magnetoresistive effect has been associated with the existence of Mn-rich clusters with the Cu$_2$AlMn-structure. The effect of an appl…
Ni$_2$Mn$_{2-y}$In$_y$ alloys transform from the martensitic $L1_0$ antiferromagnetic ground state near $y = 0$ to austenitic ferromagnetic $L2_1$ Heusler phase near $y = 1$ due to doping of In impurity for Mn. The off stoichiometric alloys prepared by rapid quenching are structurally metastable and dissociate into a mixture of $L2_1$ (Ni$_2$MnIn) and $L1_0$ (NiMn) phases upon temper annealing. Despite this structural disintegration, the martensitic transformation temperature remains invariant in the temper annealed alloys. Investigations of the local structure of the constituent atoms reveal …
