A phenomenological fitting curve for the magnetocaloric effect of materials with a second-order phase transition

摘要

The magnetic entropy change of poly crystalline samples Gd, La(Fe_(0.92)Co_(0.08))_(11.83)Al_(1.17), LaFe_(10.8)Si_(2.2), Mn_5Ge_(2.7)Ga_(0.3), Nd_2AlFe_(13)Mn_3, and TbCo_2 with a second-order phase transition has been investigated. A uniform phenomenological function that describes the magnetic entropy change is found for these materials. This could be of great benefit for the design of magnetic refrigerators. The field dependence of the critical exponent for the variation in the maximum entropy change with field is studied. The critical exponent value of 2/3, which is predicted by the mean field theory, is only satisfied for moderate field values. The refrigerant capacity is analyzed and compared to the predictions of the fitting function.