Micromechanical detectors for local field measurements based on ferromagnetic resonance (invited)

Ferromagnetic resonance (FMR) measurements were performed on micrometer-size thin-film samples deposited onto a micromechanical cantilever detector. The FMR response is coupled to cantilever motion in one of three ways: (1) By measuring the change in torque on the sample in a uniform field; the FMR precession reduces the static magnetic moment of the sample with a resultant change in torque. (2) By measuring the damping torque acting on the FMR precession. (3) By measuring the energy absorbed in FMR using a bimaterial cantilever as a calorimeter sensor. Our instrument is capable of measuring the FMR response in permalloy samples as small as 2 x 10(-11) cm(3) in ambient conditions with a signal-to-noise ratio of 100. In addition we demonstrate that this system can be used as a quantitative scanning probe magnetic field microscope. Using the magnetic field sensitivity of the FMR response in a small ferromagnetic particle, we have achieved 50 A/m field resolution on 20 mum length scales. Both dc fields and microwave fields were imaged. (C) 2001 American Institute of Physics.