Magnetocaloric effect in MnCoGe alloys studied by first-principles calculations and Monte-Carlo simulation

Abstract

The magnetocaloric effect in orthorhombic MnCoGe1−xCux (x = 0.0–0.35) alloys are investigated by combining density functional theory (DFT) and Monte-Carlo simulation. The long-range interactions of the magnetic exchange coupling constants evaluated by the DFT calculations are considered for the Monte-Carlo simulation. The magnetic phase transition temperature is estimated by the divergence of the specific heat, and the isothermal entropy change is computed by integrating the isothermal magnetization curves with the Maxwell relation. The magnetic exchange coupling constants of the Mn-Mn pairs is decreased significantly with increasing of the concentration of Cu from 0.0 to 0.35, resulting in the rapid decrease of the Curie temperature from 618 K to 28 K. Not only the Curie temperature of the MnCoGe alloy is controllable by changing the concentration of Cu at Ge site, but also the magnetocaloric properties such as isothermal magnetic entropy change and relative cooling power are strongly dependent on the concentration of Cu.