Magnetoresonance Research of Cox(Al2O3)1-x Nanogranular Films in the Vicinity of Magnetic Phase Transition

The ESR response of 35-40 GHz band from nanostructure Co
_x
(Al
₂
O
₃
)
_1-x
was analyzed. The linewidth increases while the Co concentration decreases. The magnetization of saturation drops to zero when Co concentration decreases up to concentration of Co falls up to metal-dielectric threshold. The magnetic phase transition from ferromagnetic to superparamagnetic state has been detected in the vicinity of the metal-dielectric transition.