Caracterização estrutural e magnetotérmica do composto GdGa

Abstract

The magnetocaloric effect, which is the basis of solid state magnetic cooling, is characterized by two thermodynamical quantities: the isothermal entropy change ( Δ ST ) and the adiabatic temperature change( ΔTad ); which are generally obtained under variations in the intensity of an applied magnetic field. In this work we use the heat flux technique developed at the Laboratorio de Metais e Ligas (LML) of the Gleb Wataghin Institute of Physics/University of Campinas (IFGW/UNICAMP) to obtain the specific heat curves and, consequently, the isothermal entropy change. In order to achieve this goal, we performed some studies aiming the structural and magnetic characterization of a polycrystalline sample. X-ray elastic scattering measurements were performed in Multi-User laboratories available at the Institute of Physics of Universidade Federal Fluminense (IF/UFF) and the Brazilian Center for Research in Physics (CBPF). In addition, magnetic measurements were performed at the Laboratory of Magnetism and Magnetic Materials of the IF/UFF. The samples produced did not show any structural phase transition in the considered temperature range. As reported in the literature, GdGa compound presents a spin reorientation transition at low temperatures, which is suppressed by relatively low magnetic fields (of the order of 102 Oe). The obtained entropy change Δ ST and specific heat Cp were and compared with available experimental data in the literature.