Magnetocaloric effect of perovskite manganites La0.7□0.1Ca0.2MnO3

The magnetocaloric properties of the polycrystalline manganites La-0.7 square 0.1Ca0.2MnO3 based on magnetic and resistivity measurements were investigated. Firstly, the equation Delta S = -alpha f(0)(H) [delta Ln(rho)/ delta T]H dH relates magnetic order to the transport behavior of the compounds. The relation between rho and M was found to maintain the form of q = rho(0) exp(-M/alpha) for temperatures near and slightly below T-C. This result reveals the important effect of magnetic polarons on the transport properties. It is obvious that magnetic disorder, characterized by Delta S-M, affects the magnetic polarons, while the latter influence the electronic transport properties, which may be the underlying reason for the salient Delta S-M-rho relation. On the other hand, based on a phenomenological model, the value of the magnetocaloric effect has been determined from the calculation of magnetization as a function of temperature under different magnetic fields M (T, H). This study also provides an alternative method to determine magnetic entropy change on the basis of magnetic and resistivity measurements. (C) 2015 Elsevier B.V. All rights reserved.