A New Phenomenon on the Surface of FINEMET Alloy
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O R I G I N A L PA P E R
A New Phenomenon on the Surface of FINEMET Alloy O. Životský · L. Klimša · A. Hendrych · Y. Jirásková · J. Buršík
Received: 5 November 2012 / Accepted: 30 November 2012 / Published online: 19 December 2012 © Springer Science+Business Media New York 2012
Abstract This paper is devoted to the analysis of quadratic magneto-optical effects (QMOKE) newly observed at the surface of FINEMET-type Fe73.5 Si13.5 Nb3 Cu1 B9 ribbons annealed at temperatures of 733 K and 743 K. A strongly inhomogeneous surface microstructure detected by grazing incident X-ray diffraction (GIXRD), scanning (SEM) and transmission (TEM) electron microscopy is responsible for amplitude and sign changes of the QMOKE in different sample places. Signals in saturation determined by an 8-directional method confirm the prevailing influence of ML MT contributions at some places of a surface and of ML2 − MT2 at other ones, where ML and MT are in-plane longitudinal and transversal magnetization components. This behavior is explained by random orientation of nanocrystals and/or clusters of the nanometer size (typically units of nm) in the surface layers. The maximal QMOKE magnitude in saturation reaches at some places as much as 0.2 mrad, which is approximately three times lower than the highest contribution observed in Co2 FeSi Heusler compounds.
O. Životský () · L. Klimša · A. Hendrych Institute of Physics, VŠB-Technical University of Ostrava, Ostrava 70833, Czech Republic e-mail: [email protected] O. Životský · A. Hendrych Nanotechnology Centre, VŠB-Technical University of Ostrava, Ostrava 70833, Czech Republic Y. Jirásková · J. Buršík Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Brno 61662, Czech Republic Y. Jirásková CEITEC IPM, Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Brno 61662, Czech Republic
Keywords FINEMET · Quadratic magneto-optical Kerr effects · Nanocrystalline · Surface microstructure
1 Introduction Quadratic magneto-optical effects (QMOKE) have been discovered in 1997 by Postava et al. [1] and they have shown new remarkable contributions resulting in the asymmetric MOKE hysteresis loops observed in Fe/MgO systems. It was found that asymmetries coming from QMOKE are superimposed on the linear magneto-optical contributions and exhibit an even dependence on an applied magnetic field. Huge QMOKE have been later observed in permalloy/Ta films [2], diluted magnetic semiconductors [3], and Co-based Heusler compounds [4–6], where the highest QMOKE amplitude, corresponding to about 0.5 mrad, was measured. Further theoretical and practical investigations of these effects have supplied new information about (i) their proportionality to two mixed terms ML MT and ML2 − MT2 [4, 7], where ML and MT are in-plane longitudinal and transversal magnetization components parallel and perpendicular to the plane of light incidence, respectively, (ii) magnetic anisotropy and film thickness dependence [3, 7], and (iii) their size related to the spin-orbit coupling
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