Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

High field magnetization measurements up to 60 T on free powder samples from GdCo_12-xFe_xB₆ (x = 0-3) compounds are reported. The data were used to evaluate the microscopic exchange interaction integral, J_Gd-3d, between Gd and 3d (Co,Fe) spins. The systems are ferrimagnets; they order magnetically between T_C = 95 K for x = 3 and T_C = 165 K for x = 0. The low temperature magnetization curves as well as the temperature dependence of intrinsic magnetic parameters are determined by magnetic measurements in pulsed magnetic field. The average magnetic moment µ_Co+Fe per mean transition metal atom (Co + Fe) is small and increases with increasing Fe concentration from 0.44 µ _B for x = 0 to 0.51 µ_B for x = 3 at T = 4 K. From high field magnetization curves, a value of J_Gd-3d/k_B = -4.65 K is derived for x = 0, whereas mean field approximation yields a much larger 3d-3d exchange integral of J_Co-Co/k_B = 105 K. The obtained results reveal an increase of J_Gd-3d/k_B with Fe concentration. For x = 0.5, the intersublattice coefficient n_Gd-3d is found to keep an almost constant value of 5.87 ± 0.13 T*f.u.*µ_B ^-1 whatever the temperature in the 2 to 60 K range.