Ferromagnetic Resonance Detection with a Torsion-mode Atomic-force Microscope
M. Loehndorf, John M. Moreland, Pavel Kabos
We have developed a ferromagnetic resonance (FMR) instrument based on a torsion-mode atomic-force microscope (AFM). The instrument measures the torque on a magnetized thin film in a static out-of-plane field perpendicular to the film surface. The magnetic film is deposited outo an AFM microcantilever. FMR measurements are performed at a fixed microwave frequency of 9.15 GHz with a sweeping in-plane field. At the FMR condition, the change in the average in-plane magnetization of the film is at a maximum corresponding to a maximum change in the torque on the AFM cantilever. Our instrument is capable of measuring fluctuations of in-plane magnetization of 63.3 A/m of NiFe film samples with a total volume of 1.1x10-10 cm3. Given a signal-to-noise ratio of 40, we estimate a magnetic moment sensitivity of 1.7 x 10-16 A/m2.