Effect of Dy substitution on magnetic properties and magnetocaloric effects of Tb₆Co_1.67Si₃ compounds

The magnetic and magnetocaloric properties of (Tb_1 - xDy_x)_6Co_1.67Si₃ (0 \le x \le 0.8) have been experimentally investigated. The compounds exhibit a Ce_6Ni₂Si₃-type hexagonal structure and undergo a second-order magnetic transition. The Curie temperature decreases from \sim 187 K to 142 K as the content of Dy grows from 0 to 0.8. The maximal magnetic entropy change, for a field change of 0--5 T, varies between \sim 6.2 and \sim 7.4 J/kg\cdotK, slightly decreasing when Dy is introduced. The substitution of Dy leads to a remarkable increase in refrigeration capacity (RC). A large RC value of \sim 626 J/kg is achieved for x=0.4 under a field change of 0--5 T.