Magnetocaloric effect and its implementation in critical behaviour study of La0.67Ca0.33Mn0.9Fe0.1O3

The magnetocaloric effect (MCE) and the field dependence of the magnetic entropy changes in the perovskite-type La0.67Ca0.33Mn0.9Fe0.1O3 were studied using the phenomenological model. The model parameters were determined from the magnetization data adjustment and used to give better fits to magnetic transition and to calculate the magnetocaloric properties. The entropy curves have been observed to behave a symmetrical broadning of Delta S (M) peak with the increase in magnetic field. The values of maximum magnetic entropy change, full-width at half-maximum, relative cooling power (RCP) and the refrigerant capacity (RC), at several magnetic field variations, were calculated. The maximum magnetic entropy change of 1.17 J kg(-1) K-1 was obtained for 3 T. The theoretical calculations were compared with the available experimental data. The results were found to be in good accordance. The critical exponents associated with ferromagnetic transition have been determined from the MCE methods. By using the field dependence of Delta S (max) a parts per thousand a (mu (0) H) (n) and the RCP a parts per thousand v (mu (0) H) (w) , the critical behaviour of La0.67Ca0.33Mn0.9Fe0.1O3 was investigated. From the analysis of the relationship between the local exponent n and w, other exponents beta, gamma and delta were calculated. Our results indicated that the ferromagnetic coupling in the La0.67Ca0.33Mn0.9Fe0.1O3 can be well described by the 3D Heisenberg model. This reflects an existence of ferromagnetic short-range order in the sample.