MCE_of_EuCu2P2-CPB-Revised(4)

ones, the magnetization M tends to be saturated at low field. A large reversible MCE is expected around the transition temperature where the magnetization rapidly changes with varying temperature. Since the MCE have a strong correlation with the order of the corresponding magnetic phase transition, it is important to understand the nature of magnetic transition in EuCu1.75P2 compound. According to Banerjee criterion, [24] the magnetic transition is of a second order if all the H/M versus M2 curves (also named as Arrott plot) have positive slope. On the other hand, if some of the H/M versus M2 curves show negative slope at some point, the magnetic transition is of the first order. To understand the order of the magnetic transition in EuCu1.75P2, the Arrott-plots H/M vs. M2 at some selected temperatures for EuCu1.75P2 are plotted in Fig. 3. Neither the inflection point nor negative slopes can be observed, providing the occurrence of a second order magnetic transition for EuCu1.75P2 from paramagnetic to ferromagnetic.

The second-order magnetic phase transition around the Curie point is characterized by a set of critical exponents, (associated with the spontaneous magnetization Ms), associated with the initial magnetic susceptibility ), and (associated with the critical magnetization isotherm at TC). The mathematical definitions of those exponents from magnetization measurements are given below: [25]

Ms T lim M M0 , 0,T TC (1)

H 0

0 1 T lim H/M h0/M0 , 0,T TC (2) H 0

M XH1/ , 0,T TC (3)

where M0, ho, and X are the critical amplitudes, and =(T TC)/TC is the reduced temperature. The fitting procedure is as follows. By selecting initial values for and , we first plot M1/ versus (H/M)1/ . Then we determine Ms from the intersection of the

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