부산대학교 도서관

We report on the magnetic and thermal properties [magnetization, specific heat, thermal expansion, magnetostriction, and magnetocaloric effect (MCE)] for the three multicomponent systems Tb x Dy y Gd z Co 2 , Tb x Dy y Ho z (Co, Fe) 2 , and Tb x Dy y Er z (Co, Fe) 2 ( $x + y + z = 1$ ). We show that for Tb x Dy y R z Co 2 , the Curie temperatures, $T_{\rm {C}}$ (which ranged from 130 to 300 K), and order of the phase transition (first or second order) could be controlled by composition. The highest MCE values (the adiabatic temperature change $\Delta T_{\rm ad}= 2.2$ –2.3 K at $\mu _{0} \Delta {\rm H}= 1.8$ T) were observed for the compounds exhibiting the transitions of the first order. Giant volume magnetostriction of 1500–2000 and 500–600 ppm is demonstrated at a field of $\mu _{0} {\rm H} = 10$ and 1.2 T, respectively. Structural and magnetic entropy contributions to the total isothermal entropy change are estimated for Tb x Dy y R z Co 2 . Regular recurrence and/or change of the physical properties across the varied composition of the compounds allows us to find the materials with desired magnetic characteristics, such as $T_{C}$ , MCE, and magnetostriction, to use them in practice.