Longitudinal and Polar MOKE Magnetometry of Magnetoresistive Cobalt Thin Films Prepared by Thermal Evaporation

Cobalt films of thickness 21, 29 and 68 nm were prepared by thermal evaporation with a deposition rate around 0.3 nm/s. Their hysteresis loops from longitudinal and polar magneto-optic Kerr effect (MOKE) magnetometry differed from typical characteristics of uniaxial magnetic anisotropy but still indicated the preference of in-plane anisotropy over perpendicular anisotropy. The longitudinal hysteresis loop of the 68 nm-thick film was decidedly in a transcritical state signified by an enhanced coercive field. Changing the angle (θ) between the 2500 Oe-magnetic field and the current gave rise to the change in electrical resistance (Rθ) of 29 nm-thick film and the plot between Rθ and cos2θ could be linearly fitted. The changes in resistance due to this anisotropic magnetoresistance (AMR) effect ranged from -0.08 % (θ = 90°) to +0.04 % (θ = 0°).