Magnetic anisotropy of glide-distorted fcc and of bcc ultrathin Fe/Cu(001) films.

Abstract

The effective anisotropy fields, ${H}_{\mathrm{eff}}$, of Fe films of 2 to 15 monolayers thick grown on Cu(001) were measured at 100 K for two growth conditions; 100 K growth with a room temperature anneal and room-temperature growth. First-order anisotropy constants, ${K}_{v}$ and ${K}_{s}$, are derived for the thickness independent anisotropy energy term and the thickness dependent anisotropy energy term, respectively. For 100 K growth, ${K}_{v}$ for the glide-distorted fcc Fe film is two orders of magnitude larger than for the bcc Fe film and g30 times larger than for bulk bcc Fe. The fcc film has ${K}_{s}=0.26$ ergs/${\mathrm{cm}}^{2}$, compared to 0.94 ergs/${\mathrm{cm}}^{2}$ for the bcc Fe film. The perpendicular easy axis in the glide-distorted fcc Fe, for either growth temperature, is observed only because both ${K}_{v}$ and ${K}_{s}$ result in large perpendicular anisotropy energies. A conversion to an in-plane easy axis occurs as the thickness dependent anisotropy energy decreases with increasing Fe thickness in the bcc phase and is not directly a result of the phase transformation to bcc Fe. Room-temperature growth gives similar anisotropy constants.