HARD AXIS MAGNETIZATION OF ULTRATHIN NI(111)/W(110) IN UHV A NEW SET-UP FOR SMOKE

We used a new set-up to measure the magneto-optic Kerr rotation of ultrathin ferromagnetic films in ultrahigh vacuum. A magnetic field of up to 1.4 T can be applied at the sample in situ and oriented either parallel or normal to the plane of the film. With the magnetic field oriented perpendicular to the plane of the film we recorded hard axis magnetization curves for 10 to 30 angstrom Ni(111) films on W(110) at room temperature. From this we determined the out-of-plane anisotropy field H(an)(30 angstrom) = 5.93 kG and H(an)(10 angstrom) = 10.3 kG. The magnetocrystalline anisotropy determined from H(an) is negative, thus favouring the orientation of the magnetization in the film plane. With the external field in the plane we observed square hysteresis loops along the W[001] direction. The in plane anisotropy was estimated from the coercive fields measured along the easy direction W[001].