MAGNETOOPTIC KERR-EFFECT MEASUREMENTS ON FE3-XCOXSI LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-2.5) EPITAXIALLY STABILIZED ON SI(111)

200 Angstrom thick Fe3-xCoxSi (0 less than or equal to x less than or equal to 2.5) films have been epitaxially grown on Si(111) by co-depos ition at room temperature. Low- and medium-energy electron diffraction indicate the formation of cubic silicides with a crystallinity compar able to that of epitaxial alpha-Fe on Si(111). These silicides form a random alloy as evidenced by the lack of DO3-type long-range order, us ually observed in the Fe3Si stoichiometric compound. Using ex situ mag neto-optic Ken effect, hysteresis curves for different magnetic field directions have been measured at room temperature. The data demonstrat e ferromagnetic behavior with strong in-plane uniaxial anisotropy in s pite of the threefold symmetry of the cubic structure of these Fe3-xCo xSi silicides. The easy axis is found to be parallel to the [-101] dir ection.