Investigation of Griffiths-like phase at low temperature in a new magnetocaloric compound, Al2Mn2O7

Abstract Al 2 Mn 2 O 7 was prepared by the ceramic method with M n O 2 and A l 2 O 3 as precursors. X-ray diffraction revealed that the compound crystallized as a monoclinic structure with space group P2/m. Magnetization measurements revealed a ferromagnetic transition near 35 K and features consistent with the appearance of a Griffiths-like phase. From the study of magnetic properties in terms of Arrott plots, it was observed that the phase transition is of second order. The analysis of the variation of the magnetic entropy revealed a magnetocaloric effect of 4.5 J/kg K near the hydrogen liquefaction temperature for a field change of 5 T with a relative cooling power of 67 J/kg. Critical isotherm analyses indicated that the mean field model is the most appropriate model for this compound.