HIGH-SENSITIVITY FERROMAGNETIC-RESONANCE MEASUREMENTS ON MICROMETER-SIZED SAMPLES

Ferromagnetic resonance measurements were taken on a 4 mu m diam disk using a planar microwave transmission line device. The absorption mode s of a sample placed on this devise can be measured by monitoring the microwave power transmitted across the device while a swept magnetic f ield varies the sample absorption through resonance. Results for the d isk, which was etched from a 105 nm thick amorphous Fe80B15Si5 film, f ollowed the Kittel model over the frequency range from 2 to 20 GHz, in agreement with parameters measured on 5 mm diam disks by a microwave cavity. These results indicate the device has a sensitivity of 3x10(9) . Delta H spins, almost two orders of magnitude better than microwave cavity measurements. (C) 1997 American Institute of Physics.