Investigation of the Field-Induced Phase Transitions in the (R,R′)2Fe14B Rare-Earth Intermetallics in Ultrahigh Magnetic Fields

In this work, we perform a comparative study of the magnetization behavior of four series of compounds R ₂ Fe ₁₄ B and their hydrides R ₂ Fe ₁₄ BH _5.5 , and the compositions (Nd _0.5 R _0.5 ) ₂ Fe ₁₄ B and their hydrides (Nd _0.5 R _0.5 ') ₂ Fe ₁₄ BH _5.5 with R and R' = Ho, Er, and Tm. The magnetization is measured in pulsed magnetic fields up to 58 T and in megagauss fields up to 135 T at 5 K. The first and second critical fields of the field-induced transitions, H _c1 and H _c2 were estimated analytically and the results were verified against experimental data. We find that hydrogenation of R ₂ Fe ₁₄ B and (Nd _0.5 R _0.5 ') ₂ Fe ₁₄ B reduces drastically the H _c1 and H _c2 values and, as a consequence, the intersublattice R-Fe exchange interaction parameter λ.