Magnetocaloric effects of binary rare earth mononitrides, GdxTb1−xN and TbxHo1−xN

We have synthesized GdxTb1−xN and TbxHo1−xN (x = 0, 0.25, 0.5, 0.75 and 1) by the carbothermic reduction performed in a nitrogen gas stream. GdN and TbN have been completely miscible with each other as well as TbN and HoN. As x was changed from 0 to 1, the Curie temperature increased monotonously from 18.5 to 43.8 K for TbxHo1−xN and from 43.8 to 61.2 K for GdxTb1−xN. The magnetocaloric effects have been evaluated by calculating the magnetic entropy changes from the magnetization data sets measured at different applied fields and temperatures. In any composition x, the magnetocaloric effects of GdxTb1−xN and TbxHo1−xN are larger than those of GdxDy1−xN. Therefore, GdxTb1−xN and TbxHo1−xN are promising magnetic refrigerant materials for hydrogen liquefying system working below liquid nitrogen temperature.