Investigation of the field-induced phase transitions in the (R,R’)2Fe14B rare-earth intermetallics in ultra-high magnetic fields

In this work, we perform a comparative study of the magnetization behavior of four series of compounds R2Fe14B and their hydrides R2Fe14BH5.5, and the compositions (Nd0.5R0.5)2Fe14B and their hydrides (Nd $_{0.5}\text{R}^\prime _{0.5})_{2}$ Fe14BH5.5 with R and $\text{R}^\prime =$ 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 R2Fe14B and (Nd $_{0.5}\text{R}^\prime _{0.5})_{2}$ Fe14B reduces drastically the $H_{c1}$ and $H_{c2}$ values and, as a consequence, the intersublattice R–Fe exchange interaction parameter $\lambda $ .