Novel torque magnetometry for uniaxial anisotropy constants of thin films and its application to FePt granular thin films

A technique based on torque magnetometry is proposed for precise determination of the uniaxial magnetic anisotropy constant, K u, of perpendicularly magnetized thin films, in particular for K u larger than 106 J/m3, by electrical detection of the anomalous Hall effect and exact determination of the magnetic field direction. This technique can measure the K u value of several-nanometer-thick polycrystalline films. Further, the K u value of FePt–C granular films, which are expected to be useful for high-density magnetic recording media, is evaluated. The intrinsic K u value of 4-nm-thick FePt–C thin films fabricated at 450 °C is approximately 3 MJ/m3 for carbon contents up to 34 vol % C.