Ferromagnetic resonance spectroscopy with a micromechanical calorimeter sensor

We describe a new type of ferromagnetic resonance (FMR) spectroscopy that i s based on a calorimeter sensor. We use an atomic force microscopy cantilev er coated with a ferromagnetic thin film as a bimaterial sensor to measure absorption of microwaves at 9.17 GHz. The spectra show a peak in the cantil ever deflection as a function of applied magnetic field corresponding to a peak in the absorbed microwave power that occurs at the FMR resonance of th e ferromagnetic film. The saturation magnetization M-eff and the damping fa ctor alpha were determined from the FMR microwave absorption spectra for Co , NiFe, and Ni thin films. The data correlate well with conventional FMR sp ectra taken with a tuned cavity spectrometer. Our instrument can detect mag netic moments as small as 1.3x10(-12) A m(2) (1.3x10(-9) emu) with prospect s for sensitivity improvements to the 1x10(-16) A m(2) (1x10(-12) emu) leve l. The technique provides a potentially superior way to make quantitative m easurements of saturation magnetization of thin-film samples with very smal l total magnetic moments. [S0034-6748(00)02908-7].