MICROWAVE-ABSORPTION IN SINGLE-DOMAIN PARTICLES INVOLVING 1ST-ORDER AND 2ND-ORDER UNIAXIAL MAGNETIC-ANISOTROPY CONSTANT

The ferromagnetic resonance absorption is calculated for powder assemblies of non-interacting magnetically uniaxial particles involving the anisotropy constants K1 and K2. It is shown that both constants can be obtained by FMR separately within a relative error of the second-order anisotropy constant \DELTAK2\ = \0.01 K1\. This determination method is applied on Co2+/Ti4+- and Zn2+/Ti4+-substituted barium ferrite with an amount of substitution of 0 less-than-or-equal-to x less-than-or-equal-to 1.25. For both substituted barium ferrite powders it is found that K2 is less than the 1% of K1. Consequently the decrease of the anisotropy field strength with substitution must be effected by the decrease of K1 alone.