Hysteresis loop of planar Hall effect in CoCr films

Micrometer devices of Co85Cr15 film with Hall bar shape were made using standard electron beam lithography and lift-off process. The film was thermally deposited without bias field and the sample was kept at room temperature during evaporation. The Hall voltage, measured at room temperature, showed square hysteresis loops with an external magnetic field applied in the direction close to the film plane. Based on the variation of the Hall voltage measured under different directions of external magnetic field, the magnetic easy axis was verified to be along the long axis of the device. The formation of the easy axis along the narrow wire due to the physical confinement as an intrinsic mechanism is discussed.