Critical evolution of spin-reorientation transition in magnetic Co_xNi_1-x/Cu(100) films upon precise variation of d-band filling

The ultrathin Co_xNi_1-x/Cu(100) alloy films with low Co concentration x≤10% was prepared for probing the effect of the d-band filling on the magnetic behavior. The perpendicular magnetization was observed only for films with x<10%. The spin-reorientation transition from the in-plane to perpendicular orientation was found to be extremely sensitive to the Co concentration. The critical thickness for the spin reorientation transition was changed drastically from 7.5 to 17.5 ML by varying x from 0 to 8 %. Since no significant change in structure and surface morphology was accompanied, these findings may be attributed to the critical influence of the d-band filling on the magnetic anisotropy at variation of alloy composition.