Micromechanical Detectors for Local Field Measurements Based on Ferromagnetic Resonance
Albrecht Jander, John M. Moreland, Pavel Kabos
Ferromagnetic resonance (FMR) measurements were performed on micron-size thin-film samples integrated onto a micromechanical detector. The FMR response is coupled to cantilever motion in one of three ways. 1) Measure 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) Measure the damping torque acting on the FMR precession. 3) Measure the energy absorbed in FMR using a bimaterial cantilever as calorimeter sensor. Our instrument is capable of measuring the FMR response in NiFe samples as small as 2x10-11 cm3 in ambient conditions with a signal-to-noise ratio of 100. In addition we have demonstrated 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 mm length scales. Both dc fields and microwave fields were imaged.