Efeito magnetocalórico na série R1-xR'xAl2 (R = Ho, Dy; R' = Tm, Dy, Tb, Er)

Abstract

In this work the magnetic and magnetocaloric properties of compounds 𝑅1−𝑥𝑅𝑥′ 𝐴𝑙2 (𝑅=𝐻𝑜,𝐷𝑦;𝑅′= 𝑇𝑚,𝐷𝑦,𝑇𝑏,𝐸𝑟) were studied in which we used a theoretical model whose hamiltonian includes as exchange between the 𝑅−𝑅, 𝑅’−𝑅’ e 𝑅−𝑅’ ions, in addition to the crystalline electric field and Zeeman effects. All theoretical results were compared with early measurements from the literature or from collaborations with the experimental group at the Ames Laboratory at Iowa State University. In order to reproduce the experimentally observed ferromagnetic ordering global temperatures and the spin reorientation transition temperatures, as the concentration x varies, as desirable exchange between 𝑅−𝑅, 𝑅’−𝑅’ and 𝑅−𝑅’ were defined as free parameters and adjusted to match the experimental results for each compound. We were able to satisfactorily model the magnetocaloric properties of the entire series, describing the experimental results.