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

摘要: A negative-positive-negative switching behavior of magnetoresistance (MR) with temperature is observed in a ferromagnetic shape memory alloy ${\text{Ni}}_{1.75}{\text{Mn}}_{1.25}\text{Ga}$. In the austenitic phase between 300 and 120 K, MR negative due to $s\text{\ensuremath{-}}d$ scattering. Curiously, below K positive, while at still lower temperatures martensitic phase, again. The positive cannot be explained by Lorentz contribution related magnetic transition. Evidence for this obtained from ab initio density-functional theory, decrease magnetization resistivity upturn K. Theory shows that ferrimagnetic state antiferromagnetic alignment local moments Mn atoms energetically favored ground state. there are two competing factors govern behavior: dominant trend up saturation field electron scattering twin domain boundaries weaker nature exhibits hysteresis heating cooling first-order