Study on the magnetothermal properties of the D y 1 - x T b x A l 2 series of compounds

In this work, we developed a theoretical model Hamiltonian, in the mean field approximation, to describe the magnetic and magnetocaloric behavior of the series of compounds D y 1 - x T b x A l 2 ( x = 0.00 , 0.15 , 0.25 , 0.30 , 0.35 , 0.40 and 0.75 ) . We adjusted the exchange parameters λ D y D y , λ T b T b , and λ D y T b to obtain the spin reorientation temperatures T S R and the critical temperature T C for each compound in the series. The results obtained by the Hamiltonian model agree satisfactorily with the experimental results. The heat capacity curves with and without an applied magnetic field, adiabatic temperature variation and isothermal entropy variation were modeled and compared with the experimental data. As the experimental results show, our model was also able to reproduce the change in the spin reorientation process: a first order spin reorientation transition appears for concentrations x = 0.15, 0.25, 0.30, 0.35, and no spin reorientation transitions after x = 0.40.