Variation of the intersublattice exchange coupling due to hydrogen absorption in Er_2Fe_(14)B: A high-field magnetization study

摘要

Single crystals of a series of hydrides Er_2Fe_(14)BH_x (x<2.5) have been produced and studied in pulsed magnetic fields up to 60 T. The magnetization curve of Er_2Fe_(14)B in the easy direction [100] features a stepwise anomaly at about 45 T, corresponding to the first-order phase transition. A similar magnetization jump is also present in the curve along [110], but at a higher field, ～52 T. The [100] data of the parent and hydrogen-charged Er_2Fe_(14)BH_x with x = 0.25, 1.5, 2.5 were used to deduce the Er-Fe molecular field H_(mol) as a function of hydrogen content x. After moderate initial decrease, H_(mol)(x) drops abruptly above x = 1.5. Hydrogenation results in a 12% reduction of the Er-Fe molecular field in Er_2Fe_(14)BH_(2.5) as compared to Er_2Fe_(14)B. For reference, influence of hydrogen on H_(mol) in an Er_2Fe_(17)-H system is also presented.