Magnetocaloric properties and Griffiths phase of ferrimagnetic cobaltite CaBaCo₄O₇

【摘要】 We present a study on the magnetocaloric properties of a CaBaCo₄O₇ polycrystalline cobaltite along with research on the nature of magnetic phase transition. The magnetization as a function of temperature identifies the ferrimagnetic to paramagnetic transition at a Curie temperature of 60 K. Moreover, a Griffiths-like phase is confirmed in a temperature range above T_C. The compound undergoes a crossover from the first to second-order ferrimagnetic transformation, as evidenced by the Arrott plots, scaling of the universal entropy curve, and field-dependent magnetic entropy change. The maximum of entropy change is 3 J/kg·K for ?H = 7 T at T_C, and a broadening of the entropy peak with increasing magnetic field indicates a field-induced transition above T_C. The analysis of the magnetic entropy change using the Landau theory reveals the second-order phase transition and indicates that the magnetocaloric properties of CaBaCo₄O₇ are dominated by the magnetoelastic coupling and electron interaction. The corresponding values of refrigerant capacity and relative cooling power are estimated to be 33 J/kg and 42 J/kg, respectively.更多还原

【Abstract】 We present a study on the magnetocaloric properties of a CaBaCo₄O₇ polycrystalline cobaltite along with research on the nature of magnetic phase transition. The magnetization as a function of temperature identifies the ferrimagnetic to paramagnetic transition at a Curie temperature of 60 K. Moreover, a Griffiths-like phase is confirmed in a temperature range above T_C. The compound undergoes a crossover from the first to second-order ferrimagnetic transformation, as evidenced by the Arrott plots, scaling of the universal entropy curve, and field-dependent magnetic entropy change. The maximum of entropy change is 3 J/kg·K for ?H = 7 T at T_C, and a broadening of the entropy peak with increasing magnetic field indicates a field-induced transition above T_C. The analysis of the magnetic entropy change using the Landau theory reveals the second-order phase transition and indicates that the magnetocaloric properties of CaBaCo₄O₇ are dominated by the magnetoelastic coupling and electron interaction. The corresponding values of refrigerant capacity and relative cooling power are estimated to be 33 J/kg and 42 J/kg, respectively.更多还原