Ionic radius effect on the evolution of the griffiths phase and the magnetocaloric response at low temperature of A2Mn2O7 (A: Fe, Al and La).

In the present paper a comparative research study has been conducted on the magnetic and magnetocaloric response of the materials of A 2 M n 2 0 7 (A: Fe, Al and La) oxides.. The XRD refinement analysis suggests that the A 2 M n 2 0 7 oxides are crystallized in monoclinic structure with space group P 2/ m. The thermal evolution of the magnetization reveals a ferromagnetic transition and a presence of a Griffith's phase at low temperature. A 2 M n 2 0 7 oxides exhibit a clear correlation between the ionic radius r A 3 + , in the A-site, and the magnetic transition temperature and that of Griffiths. However, this correlation is not obvious for the value of the universal exponent λ. In addition, the current study reveals an increase in the Relative Cooling Power (RCP) value with a decrease in ionic radius. Furthermore, the magnetocaloric effect (MCE) value, has been found to be exploited over a wide temperature range by increasing the cationic radius r A 3 + . • The magnetic and magnetocaloric response of (A 2 M n 2 0 7 A : F e , L a a n d A l and A l 2 M n 2 0 7) materials revealed a significant link between the ionic radius r A 3 + in A-site and the magnetic transition temperature and that of Griffiths. The present research work also demonstrated that when ionic radius decreased, RCP value increased. On the other hand, the MCE is likely to be used over a broad temperature range, by increasing the cationic radius r A 3 + . [ABSTRACT FROM AUTHOR]