Magnetic moment and magnetocrystalline anisotropy of 3d-ion subsystem in R2T14B

The effect of substituting cobalt for iron on the magnetic moment, magneto-crystalline anisotropy and thermal expansion of R2(Fe1-xCox)14B single crystals (R=Y, Gd, 0≤x≤0.3) is investigated. The uniaxial magnetic anisotropy constant K1 for the 3d-subsystem passes through a maximum at T=4.2 K with increasing Co concentration. For T<0.5 Tc the temperature dependence of K1 does not possess a positive slope. The magnetic moment of the 3d-subsystem at 4.2 K does not exhibit the maximum at intermediate concentrations observed for most R(Fe, Co)-intermetallics. An explanation is presented of the changes in the magnetic properties. It is shown that the variation of the interatomic distances on thermal expansion should not affect the magnitude of the anisotropy constant of the 3d- and R-subsystems