STRUCTURAL AND MAGNETIC-PROPERTIES OF ULTRATHIN FE FILMS DEPOSITED ATLOW-TEMPERATURE ON CU(100)

Recently iron films have been grown on Cu(100) mainly using two differ ent procedures. Iron was either deposited at room temperature or at lo w temperature (around 100 K). Surprisingly enough, the magnetic proper ties of films showed a pronounced dependence upon the growth temperatu re. Therefore we have investigated magnetism, structure and morphology of iron films grown at 100 K. The measurements show a strong dependen ce of the magnetic properties on the film structure. Below 4.6 ML, Fe grows in the ferromagnetic fee phase. The film structure is characteri zed by enlarged interlayer spacings and a reconstruction pattern, whic h is indicative for an instability towards shear displacements in the [011] direction. Upon increasing thickness the perpendicular magnetiza tion switches in-plane around 4.6 ML. The reorientation is correlated with a structural transition to bcc iron. This phase grows in four dif ferent domains with Pitsch orientation, i.e. the bcc (110) plane paral lel to the Cu(100) substrate. The phase transition to bcc iron differs considerably from the martensitic mechanism effective for room-temper ature growth. Possibly a local shear displacement enables a direct tra nsition from ferromagnetic fee iron to the bcc phase. In contrast to f ilms deposited at 300 K, no antiferromagnetic fee phase is stabilized. This has a pronounced influence on the thickness dependence of the co ercivity.