Magnetic anisotropy and coercivity in MgO/Fe (t_Fe)/Ag films

Abstract
Magnetic systems with reduced dimensionality show critical features, such as perpendicular surface anisotropy, enhanced magnetic moment. We have compared the magnetic properties of the iron thin films deposited by electron beam evaporation onto MgO and glass/Ag(buffer) substrates. The steps on the MgO(001) substrates of height =4.1 nm were imagined by AFM. FMR has been employed to study the magnetic anisotropy H_K, and coercivity H_C was measured using VSM. In the iron films on MgO substrate the strong in-plane fourfold anisotropy (K₁=4.8x10⁴ J/m³ for t_Fe=23nm) was observed. The anisotropy field scales with the iron film thickness. H_C appeared to be significantly reduced in comparison with H_K (H_K=2K₁/M=10xH_C). This result was ascribed to the pinning effects occurring at the steps on the substrate surface. The iron films on glass/Ag were characterized by weak uniaxial anisotropy (Ku=0.28x10⁴ J/m³) consistent with the coercivity.