Detailed discrimination of the order of magnetic transitions and magnetocaloric effect in pure and pseudobinary Co Laves phases

Abstract

We present a study of the Banerjee criterion and its applicability to those cases in which the first- or second-order character of a magnetic phase transition is controversial. Detailed magnetization measurements on R Co 2 ( R = Er , Pr, Nd, and Dy) are analyzed in the framework of Landau theory and the Banerjee criterion. We show that, in general, a simple observation of the curvature of H / M vs. M 2 is not sufficient to determine the order of a magnetic transition. Our detailed analysis, together with a complementary calorimetric study, has also been applied to the pseudobinary solid solution Er x Pr 1− x Co 2 ( x = 0.9 , 0.8, and 0.7), in order to check its validity in an unknown, non-trivial case. Magnetization measurements on Er x Pr 1− x Co 2 compounds with x = 0.6 and 0.4 show that this analysis is restricted to single phase and unfrustrated magnets. We present also the magnetic entropy change at the transition of the studied R Co 2 compounds obtained by applying the Maxwell relations.