MCE_of_EuCu2P2-CPB-Revised(6)

magnetic field, and the temperature of the system, respectively. From the magnetization measurements made at discrete field and temperature intervals, SM can be approximately calculated by the following expression:

SM T, H iMi 1(Ti 1,H) Mi(Ti,H)H. (2) Ti 1 Ti

The temperature dependence of magnetic entropy change - SM for EuCu1.75P2 with magnetic field changes up to 7 T was calculated using equation (4) in the vicinity of its ordering temperature based on the results of magnetization isotherms, the results are shown in Fig. 6. A large magnetocaloric effect can be observed around 50 K. The maximum values of magnetic entropy change (- SMmax) reach 5.6, 10.7 and 13.3 J kg-1 K-1 for field changes of 2, 5 and 7 T, respectively. The observed large MCE in EuCu1.75P2 is believed to be related to the second order magnetic phase transition which is discussed above. The refrigerant capacity or relative cooling power (RCP) is a quality factor of a refrigerant material which is a measure of the amount of heat transfer between the cold and hot reservoirs in an ideal refrigeration cycle. The RCP is defined as the product of the maximum magnetic entropy change SMmax and full width at half maximum in SM (T) curve δTFWHM. The RCP values of EuCu1.75P2 are 101, 331 and 478 J/kg for field changes of 2, 5 and 7 T, respectively. Another important parameter for MCE materials is the temperature dependence of adiabatic temperature change Tad, which was also roughly evaluated using the SM(T) and zero-field specific heat results (Fig. 1). The temperature dependence of Tad for EuCu1.75P2 with various magnetic field changes up to 7 T are shown in Fig. 7. The overall nature of Tad as a function of temperature is remarkably similar to that of SM (T). The maximum values of adiabatic temperature change ( Tadmax) reach 2.1, 4.0 and 5.0 K for field changes of 2, 5