Magnetocaloric effect in manganites

JOAQUIN SACANELL; MARIANO QUINTERO; LUIS GHIVELDER; ANGELO M. S GOMES; ANA GABRIELA LEYVA; FRANCISCO PARISI

Valparaíso, Chile

Conferencia; Sólidos 2009; 2009

The magnetocaloric effect (MCE) is the isothermal change of the magnetic entropy and the adiabatic temperature change induced in a magnetic material when an external magnetic field is applied [1].   Methods of measuring the MCE can be divided into two main groups: direct and indirect techniques. In the indirect methods, the MCE and the magnetic entropy can be determined on the basis of heat capacity and magnetization data. In direct methods the sample temperature is recorded while the magnetic field is applied. From the large list of systems which exhibit MCE, manganese oxide based compounds, the so-called manganites, are one of the most promising systems, due to the strong coupling between their magnetic, electronic and structural degrees of freedom. Anomalies in the thermal expansion coefficients and discontinuities in the volume cell were observed in different manganites at the ferromagnetic transition temperature [2].  Structural transitions induced by a magnetic field were also observed [3]. This work is devoted to the study of the MCE in managanites. We present an alternative way to calculate the temperature change of from changes in the enthalpy which, unlike traditional methods, can be used in manganites with phase separation (the intrinsic tendency of some manganites towards the coexistence of two or more phases) [4].