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 investigated. All of the compounds crystallize in the tetragonal ThMn12 structure. The unit cell volume slightly decreases with increasing Co content for both systems. Curie temperature (T-C) almost increases linearly with increasing Co content for both systems. The maximum of saturation magnetization (M-s) appears 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 compounds are along the crystallographic c axis at room temperature. Thermomagnetic analysis shows that there exists no spin reorientation in the whole ordering temperature range. The magnetocrystalline anisotropy field B-a of Y(Fe1-xCox)(11.3)Nb-0.7 exhibits a maximum with x=0.10 at 5 K and x=0.05 at room temperature, while B-a of Ho(Fe1-xCox)(11.3)Nb-0.7 decreases monotonically with the increasing Co content at room temperature. First-order magnetization process (FOMP) has been observed in Ho(Fe1-xCox)(11.3) compounds at low temperature. (C) 2000 American Institute of Physics. [S0021-8979(00)21108-0].