Microwave Resonance Absorption in Nickel Ferrite-Aluminate

Abstract

Magnetic resonance measurements on $\mathrm{NiO}{\mathrm{Al}}_{t}{\mathrm{Fe}}_{2\ensuremath{-}t}{\mathrm{O}}_{3}$ gave $g$ values which shifted from $g>2$ to $g<2$ at approximately $t=0.7$. 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 $t=0.7$. The $g$ values have the general characteristic of decreasing in magnitude as the temperature is raised. At $t=1.75$ and -196\ifmmode^\circ\else\textdegree\fi{}C two resonant peaks were observed, one with $g=1.4$ and a new peak with $g=4.0$, while for $t=2$ (nickel aluminate) no resonance absorption was observed. The half-widths of the resonance curves increased to a maximum value at $t=0.5$ and went through a minimum in the region of $t=1.25$.