Microwave Resonance Absorption in Nickel Ferrite-Aluminate

Abstract

Magnetic resonance measurements on $\mathrm{NiO}{\mathrm{Al}}_t{\mathrm{Fe}}_{2-t}{\mathrm{O}}_3$ gave $g$ values which shifted from $g>\mathrm{}2\mathrm{}$ to $g<\mathrm{}2\mathrm{}$ at approximately $t=0.7\mathrm{}$. At this composition the dominant magnetic moment changes from the $B$ to the $A$ sites and the shift in $g$ values is believed to be correlated with the vanishing of the magnetic moment and angular momentum at different points close to $t=0.7\mathrm{}$. The $g$ values have the general characteristic of decreasing in magnitude as the temperature is raised. At $t=1.75\mathrm{}$ and -196°C two resonant peaks were observed, one with $g=1.4\mathrm{}$ and a new peak with $g=4.0\mathrm{}$, while for $t=2\mathrm{}$ (nickel aluminate) no resonance absorption was observed. The half-widths of the resonance curves increased to a maximum value at $t=0.5\mathrm{}$ and went through a minimum in the region of $t=1.25\mathrm{}$.