Tuning structural-transformation temperature toward giant magnetocaloric effect in MnCoGe alloy: A theoretical study

We propose a new model and scheme to consider the effect of structural transformation on magnetocaloric properties of Mn1-xCuxCoGe. The magnetic exchange coupling constants are estimated from first-principles calculations based on density functional theory. The magnetic phase diagram is semi-quantitatively reproduced by using mean-field approximation. The giant isothermal magnetic entropy change with the magnetostructural coupling of Mn0.89Cu0.11CoGe alloy is well reproduced by using the modified Potts model. The enhancement of magnetostructural coupling on the isothermal magnetic entropy change strongly depends on the condition of the magnetic phase transition temperature of orthorhombic and hexagonal phases.