No abstract

In our experiments of magnetic microscope and magnetic particle detection using an anisotropic magnetoresistive (AMR) sensor, we found that any nonmagnetic materials can also produce signals when they were close to the AMR senor. By simultaneously monitoring the temperature and the output signal of AMR sensor, we proved that these signals were caused by the thermal disturbance induces by the noncontact specimens.Index Terms-Anisotropic magnetoresistive (AMR), magnetic field measurement, thermal disturbance.

Ultrathin Co films were deposited on Pt͑100͒ at room temperature in ultrahigh vacuum, and investigated in situ by low-energy electron diffraction, scanning tunneling microscopy ͑STM͒, and surface magneto-optic Kerr effect. The Co film was grown into a wedge shape to provide a continuous change of the film thickness. We find that the Co film forms single-crystal ultrathin films at least up to 5 monolayers ͑ML͒. For as-grown films, we observe only in-plane magnetization. After annealing the film, the Co film develops a perpendicular magnetic anisotropy, leading to a spin reorientation transition at 2.7 ML Co thickness. STM measurements were performed at room temperature both before and after annealing the film. We found very different surface morphology and alloy formation after the film annealing, and attribute the perpendicular magnetic anisotropy to the formation of the Co-Pt alloy layer at the Co/ Pt͑100͒ interface.