High-field magnetization of single crystals of RMn₆Ge _6-xGa_x compounds with R = Tb, Er, Tm, Yb and x ≈ 1

The magnetization has been measured of single crystals of RMn ₆Ge_6-xGa_x (R = Tb, Er, Tm and Yb and x ≈ 1) compounds at 4.2 K in high magnetic fields up to 65 T applied along the main crystallographic directions. At low temperature, where the magnetocrystalline anisotropy is determined by the R contribution, these compounds exhibit easy-axis anisotropy with the c-axis as preferred moment direction. The magnetization display a variety of field-induced phase transitions which are particularly pronounced in the compounds with Tb, Er and Tm. The Yb compound exhibits the onset of a phase transition in the field region above 65 T. The results are discussed in terms of the interplay between the antiferromagnetic intersublattice R-Mn coupling and the magnetic anisotropy.