Magnetocaloric effect and magnetoresistance correlation in Ge-doped Mn2Sb

Magnetocaloric effect (MCE) and magnetoresistance (MR) in Ge-doped Mn₂Sb systems with near-room-temperature, first-order antiferromagnetic (AFM) to ferrimagnetic (FRI) transitions have been studied. They show an inverse MCE with a 3.2 J/kg-K isothermal change in entropy (∆S), and a refrigeration capacity that varies linearly up to 130 J kg^-1 for a 13 Tesla magnetic field change. MR (dominated by change in electronic structure) and ∆S (dominated by change in magnetic entropy) are shown to have similar temperature dependence but with opposite signs due to coupled electronic and magnetic changes across the transition. The ratio of the peak values of MR (%) and ∆S is found to be -5.6 (J/kg-K)^-1, which remains nearly constant for the studied range of magnetic field change. Existing data of MR and MCE in other Mn₂Sb systems (with substitution elements other than Ge) with nearby transition temperatures also show nearly same value for this ratio. Therefore, this ratio can be related to coupling between magnetic and electronic changes and will be an useful parameter for systems with such transitions.