Probing the (001) surface of magnetite crystals by second harmonic generation

• Published in: Journal of physics. Condensed matter Vol. 19; no. 39; pp. 396006 - 396006 (10)
• Main Authors: Rzhevsky, A A, Krichevtsov, B B, Su, Y, Schneider, C M
• Format: Journal Article
• Language: English
• Published: IOP Publishing 03.10.2007
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/19/39/396006

The surface structural and magnetic properties of (100)-oriented Fe3O4 bulk crystals in the high-temperature phase (centrosymmetric, Oh) have been studied by nonlinear second harmonic generation (SHG). The analysis of the azimuthal and magnetic field dependences of the SHG signal at nearly normal light incidence shows that the surface crystalline and magnetic symmetry of the samples investigated cannot be described by a point symmetry group C4v, contrary to what may be expected from the crystalline symmetry. Instead, the data are compatible with a symmetry of group m or even lower. The reasons for this discrepancy are attributed to an extreme sensitivity of the method to even small (~1 deg -2 deg ) misorientations from the (100) surface plane for this particular experimental geometry and to the presence of surface stresses induced by surface defects. In addition, we find that the magnetic contrast from Fe3O4(001) is rather large (~60-80%) and contains a contribution to the magnetization-induced second harmonic generation (MSHG) signal, which depends quadratically on the surface magnetization.