A new tool for measuring polar magneto-optical Kerr hysteresis curves at high fields and low temperatures

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Abstract
The design of a unique probe to measure the magneto-optical (MO) Kerr rotation and MO Kerr ellipticity of thin films and multilayers at high magnetic fields (0–25 T) and low temperatures (2–325 K) is described. The design of the probe is based on direct optics. Magnetic iron was used to screen the optical components from the stray field of the magnet. The equipment has sensitivity better than 0.25 mdegree at 632.8 nm and the residual background that results from the Faraday rotation in the optical components is smaller than 2 mdegree/T. The probe measures the polar MO hysteresis curve of samples with dimensions from 0.5–2 cm. Preliminary results on a 9 monolayer iron film and a single-crystalline FePt sample show the performance of this new characterization tool. This new MO magnetometer can be used in one of the resistive magnets of the National High Magnetic Field Laboratory in Tallahassee and is available for all internal and external users.