Micromechanical Torque Magnetometer for In Situ Thin-Film Measurements

We describe a new type of magnetometer based on a microelectromechanical system (MEMS) for in situ monitoring of magnetic film moment during the film deposition process. The magnetometer measures mechanical torque on a film as it is deposited onto a microscopic flexible silicon cantilever. The cantilever is excited by an external ac magnetic field and its angular displacement is proportional to the magnetic moment of the film. The instrument has a magnetic moment sensitivity of 1 10 12 Am Hz corresponding to a torque sensitivity of 4 10 16 Nm/ Hz. We were able to detect the moments of Fe films as thin as 3 nm. For thicker films (above 9 nm) we can detect thickness changes as small as 0.3 nm, corresponding to the instrument’s moment sensitivity limit.