S. R. Barman

Large negative magnetoresistance in a ferromagnetic shape memory alloy: Ni2+xMn1−xGa

5% negative magnetoresistance (MR) at room temperature has been observed in bulk Ni2+xMn1−xGa. This indicates the possibility of using Ni2+xMn1−xGa as magnetic sensors. We have measured MR in the ferromagnetic state for different compositions (x=0–0.2) in the austenitic, premartensitic, and martensitic phases. MR is found to increase with x. While MR for x=0 varies almost linearly in the austenitic and premartensitic phases, in the martensitic phase it shows a cusplike shape. This has been explained by the changes in twin and domain structures in the martensitic phase. In the austenitic phase, which does not have twin structure, MR agrees with theory based on s-d scattering model.

Theoretical prediction of shape memory behavior and ferrimagnetism in Mn2NiIn

Using density functional theory, we show that in Mn2NiIn a phase transition from cubic to tetragonal structure results in a lowering of the total energy, indicating occurrence of martensitic phase transition. The structural phase transition is nearly volume conserving, which is a characteristic of a shape memory alloy. The magnetic ground state is ferrimagnetic with antiparallel Mn spin moments and the total spin magnetization is 0.51μB in the martensitic phase. Thus, we predict that Mn2NiIn would behave like a magnetic shape memory alloy. The electronic structure and magnetic properties are explained by the spin polarized density of states.

Martensitic transition, ferrimagnetism and Fermi surface nesting in Mn2NiGa

The electronic structure of Mn2NiGa has been studied using density functional theory and photoemission spectroscopy. The lower-temperature tetragonal martensitic phase with c/a= 1.25 is more stable compared to the higher-temperature austenitic phase. Mn2NiGa is ferrimagnetic in both phases. The calculated valence band spectrum, the optimized lattice constants and the magnetic moments are in good agreement with experiment. The majority-spin Fermi surface (FS) expands in the martensitic phase, while the minority-spin FS shrinks. FS nesting indicates occurrence of phonon softening and modulation in the martensitic phase.

Theoretical prediction and experimental study of a ferromagnetic shape memory alloy: Ga2MnNi

We predict the existence of a ferromagnetic shape memory alloy

Valence band discontinuity at a cubic GaN/GaAs heterojunction measured by synchrotron-radiation photoemission spectroscopy

{\text{Ga}}_{2}\text{MnNi}

Influence of Ni doping on the electronic structure of Ni2MnGa

using density-functional theory. The martensitic start temperature

Magnetoresistance behavior of ferromagnetic shape memory alloy Ni 1.75 Mn 1.25 Ga

({T}_{M})

Antiferromagnetic exchange interactions in the Ni2Mn1.4In0.6ferromagnetic Heusler alloy

is found to be approximately proportional to the stabilization energy of the martensitic phase

Variation of magnetoresistance in Ni2+xMn1−xGa with composition

(\ensuremath{\delta}{E}_{\text{tot}})

(3 + 1)D superspace description of the incommensurate modulation in the premartensite phase of Ni2MnGa: a high resolution synchrotron x-ray powder diffraction study.

for different shape memory alloys. Experimental studies performed to verify the theoretical results show that