Magnetocaloric properties and Griffiths phase of ferrimagnetic cobaltite CaBaCo4O7 |
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Institution: | 1.Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;2.School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China;3.Center of Quantum Materials and Devices, Chongqing University, Chongqing 401331, China |
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Abstract: | We present a study on the magnetocaloric properties of a CaBaCo$_{4}$O$_{7}$ 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 $T_{\rm C}$. 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$\cdot$K for $\Delta H = 7$ T at ${T}_{\rm C}$, and a broadening of the entropy peak with increasing magnetic field indicates a field-induced transition above $T_{\rm C}$. The analysis of the magnetic entropy change using the Landau theory reveals the second-order phase transition and indicates that the magnetocaloric properties of CaBaCo$_{4}$O$_{7}$ 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. |
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Keywords: | magnetocaloric effect cobaltite phase transition Griffiths phase |
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