Multiple magnetic phase transitions and magnetocaloric effects of perovskite manganite

Perovskite La _0.7Ca _0.3Mn _0.9Cu _0.1O ₃ manganite was prepared and examined by X-ray diffraction. Multiple magnetic phase transitions and magnetocaloric effect were represented based on magnetic and specific heat measurements. The sample undergoes a first-order ferromagnetic - paramagnetic transition with a large thermal hysteresis, where the Arrott plots show negative slopes. A charge ordered phase occurs at T _CO = 162 K, which can be melted under a sufficiently large magnetic field ( µ ₀ H ≥ 1 T) and thus result in a spin reorientation. The step-like jump of magnetization at T _b = 42 K in warming curves is caused by a blocked state, which is overcome by applying a magnetic field and leads to a metamagnetic transition. The successive multiple magnetic phase transitions broaden the operating temperature span and contribute to a large refrigerant capacity, in spite of mediocre magnetic entropy change and adiabatic temperature change. The adiabatic temperature change and phase transition mechanism were also discussed based on the recorded specific heat data.