Magnetic, thermal and magnetocaloric studies of polycrystalline HoMnO₃ compound

Abstract

Polycrystalline HoMnO₃ (HMO) samples were prepared through the solid-state reaction method to study their magnetic, thermal and magnetocaloric properties. X-ray diffraction studies revealed that the sample crystallized in hexagonal structure with P63cm space group. Low-temperature magnetization measurements showed an anomaly at 4 K, whereas the heat capacity measurements carried out under 0 T, 2 T, 5 T and 9 T fields in the temperature region of 2–150 K exhibited three different transitions at 72 K, 33 K and 5 K. These transitions are attributed to the ordering of Mn³⁺, spin reorientation of Mn³⁺ ions and Ho³⁺ ions, respectively. Magnetic contribution to the total entropy change was also evaluated at different magnetic fields. Magnetocaloric effect (MCE) parameters such as isothermal entropy change of 2 J/kg-K, 9 J/kg-K and 16 J/kg-K were obtained at around 10 K for a magnetic field change of 2T, 5T and 9T, respectively. The adiabatic temperature change (ΔT) values are found to be 0.6 K, 3.5 K and 8.5 K, whereas the relative cooling power (RCP) is found to be 4 J/kg, 120 J/kg and 360 J/kg under 2T, 5T and 9T magnetic field change, respectively.