Phase diagram and magnetocaloric effects in Ni1-xCrxMnGe1.05

Abstract

The structural and magnetic properties of the Ni1−xCrxMnGe1.05 system (for x = 0, 0.035, 0.070, 0.105) have been studied by x-ray diffraction (XRD), differential scanning calorimetry (DSC), and magnetization measurements. A change in crystal structure from orthorhombic to hexagonal was observed in the XRD data at chromium concentrations of x = 0.035, 0.070, and 0.105. The values of the cell parameters and volume of the unit cell for orthorhombic and hexagonal phase were determined. It was found that the partial substitution of Cr for Ni in Ni1−xCrxMnGe1.05 results in a first order magnetostructural transition from antiferromagnetic to ferromagnetic (FM) at TM = 132 K for x = 0.105. A FM to paramagnetic second order transition has been observed at TC = 204 K. A magnetic entropy change of |ΔSM| = 4.5 J/kg K for ΔH = 5 T was observed in the vicinity of TC and TM for x = 0.105. The values of the latent heat (L = 2.2 J/g) and corresponding total entropy changes (ΔST = 16 J/kg K) have been determined from DSC measurements. A concentration-dependent phase diagram of transition temperatures has been constructed using the magnetic and DSC data.