Magnetic properties of R(Fe1-xCox)(11.3)Nb-0.7 (R=Y,Ho) compounds

Magnetic properties R(Fe1-xCox)(11.3)Nb-0.7 compounds have been investigate d. All of the compounds crystallize in the tetragonal ThMn12 structure. The unit cell volume slightly decreases with increasing Co content for both sy stems. Curie temperature (T-C) almost increases linearly with increasing Co content for both systems. The maximum of saturation magnetization (M-s) ap pears around x=0.2 in Ho(Fe1-xCox)(11.3)Nb-0.7 and x=0.15 in Y(Fe1-xCox)(11 .3)Nb-0.7 compounds at 5 K. The easy magnetization directions of all compou nds are along the crystallographic c axis at room temperature. Thermomagnet ic analysis shows that there exists no spin reorientation in the whole orde ring temperature range. The magnetocrystalline anisotropy field B-a of Y(Fe 1-xCox)(11.3)Nb-0.7 exhibits a maximum with x=0.10 at 5 K and x=0.05 at roo m temperature, while B-a of Ho(Fe1-xCox)(11.3)Nb-0.7 decreases monotonicall y with the increasing Co content at room temperature. First-order magnetiza tion process (FOMP) has been observed in Ho(Fe1-xCox)(11.3) compounds at lo w temperature. (C) 2000 American Institute of Physics. [S0021-8979(00)21108 -0].