Magnetic properties in epitaxial binary iron and ternary iron-cobalt silicide thin films grown on Si(1 1 1)

Abstract Binary Fe(Si 1− x Fe x ) iron and ternary Fe 3− y Co y Si iron cobalt silicide thin films (thickness : 200 A) with local CsCl structure epitaxially grown at room temperature on Si(1 1 1) have been studied through X-ray magnetic circular dichroism (XMCD) and magneto-optic Kerr effect (MOKE) vector magnetometry. The binary Fe(Si 1− x Fe x ) films have ferromagnetic properties at room temperature in the range 0.09⩽ x 3− y Co y Si films are ferromagnetic as well in the whole range 0 y 3 Si) favored by the absence of orientation dependence of the fourth-order cubic term of the magnetocrystalline anisotropy energy in (1 1 1) crystallographic plane. The easy axis corresponds invariably to the direction normal to the incidence plane of the atomic flux during evaporation. The substitution of iron by silicon in Fe(Si 1− x Fe x ) films increases the coercive field but does not strongly affect the uniaxial anisotropy constant. In Fe 3− y Co y Si alloys, a similar trend is observed and the increase of coercive force may be related to defects generated by alloying. The change of the magnetic moments of Fe and Co versus y , as obtained by XMCD, can be understood in terms of simple models.