Growth, crystalline structure and magnetic properties of ultrathin alloy films Co_xNi_1-x/Cu(1 0 0)

Magnetic ultrathin alloy films Co_xNi_1-x/Cu(1 0 0) were prepared to characterize the behavior of spin reorientation transition (SRT). With the double calibration by medium energy electron diffraction oscillation and Auger electron spectroscopy, the composition of the alloy films was controlled within an accuracy of ±0.5%, which allowed us to prepare alloy films in very low Co concentration. The critical thickness of SRT in alloy ultrathin films Co_xNi_1-x/Cu(1 0 0) was significantly delayed for x less than 10%, and for x = 10%, alloy films, at least up to 20.6 ML, always revealed in-plane anisotropy. Besides the sensitive influence of composition on SRT behavior when x ≤ 10%, the vertical interlayer distance of all the films did not show any significant difference. These results were consistent with prior theoretical calculation, in which the magnetic anisotropy was concluded to change sign abruptly while tuning a few average number of 3d electron.