Micrometer-scale magnetometry of thin Ni80Fe20 films using ultrasensitive microcantilevers

Abstract

Microcantilever torque magnetometry is used to measure quantitative M-H curves on patterned Ni80Fe20 films. The dynamic deflection method is employed, in which a small film is deposited onto a microcantilever and placed in an external magnetic field. A small orthogonal ac torque field is applied at the cantilever's resonant frequency, and the resulting torque is measured as a function of external field. Film patterning and deposition have been integrated with cantilever fabrication. Results are presented for a 5 μm×5 μm×30 μm Ni–Fe film. The measured saturated magnetic moment of the sample is 5.1±0.2×10−13 A m2 for a 100 A/m torque field. The M-H curves for the smaller films show hysteretic switching consistent with a series of stable multi-domain states. Values of the saturation magnetization are within 3% of the value measured on similar samples by ferromagnetic resonance, indicating this is a sensitive method for measuring magnetic reversal in small ferromagnetic samples.