Magnetocaloric Mn5Si3 and MnFe4Si3 at variable pressure and temperature

Abstract

The influence of hydrostatic high pressure on the crystal structures and magnetic properties of magnetocaloric Mn5Si3 and MnFe4Si3 was studied with temperature dependent synchrotron powder diffraction, neutron single-crystal diffraction and magnetization measurements. Mn5Si3 shows no indication for any pressure-induced structural phase transition up to 24.2 GPa at room temperature. MnFe4Si3 exhibits no clear indication for any phase transition at high temperatures (296 K-373 K) and high pressures. Anomalies in the lattice parameter at low temperatures indicate a structural response to magnetic ordering. The gradient of decreasing magnetic transition temperature with increasing pressure is dT C/dP ≈-15 K GPa-1. The transition temperature in MnFe4Si3 can be tuned by pressure in the temperature range relevant for applications, while pressure has hardly any detrimental influence on other key features relevant to magnetocaloric applications (the width of hysteresis, saturation magnetization, magnetocrystalline anisotropy).