* Corresponding author. Fax: #38-0572-322370. E-mail address: chizhik@ilt.kharkov.ua (A.B. Chizhik). Journal of Magnetism and Magnetic Materials 213 (2000) 19}24 Formation of noncollinear spin con"gurations during magnetization reversal in multilayered Fe/Si "lms A.B. Chizhik*, K. Fronc, S.L. Gnatchenko, D.N. Merenkov, R. Zuberek Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine, 310164 Kharkov, Ukraine Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw, Poland Received 28 July 1999 Abstract Magnetization reversal processes in Fe/Si multilayered "lms have been studied by means of the longitudinal magneto-optical Kerr e!ect at room temperature. The multilayers have been grown by DC sputtering on the single- crystal GaAs substrate. The Kerr e!ect curves had areas with an invariable or slightly varying rotation and had di!erent remanent rotation value in the zero magnetic "eld for di!erent directions of the magnetic "eld in the "lm plane. The observed features are related to the formation of stable and metastable noncollinear spin con"gurations. The experi- mental results are explained in the framework of the theory, which takes into account the competition between the bilinear exchange term on the one hand and the biquadratic exchange or cubic magnetic anisotropy terms on the other hand.  2000 Elsevier Science B.V. All rights reserved. PACS: 75.70; 75.60.E; 75.30.K; 78.20.L Keywords: Multilayers; Magnetization reversal; Magneto-optical Kerr e!ect; Spin con"gurations 1. Introduction During recent years intensive studies have been carried out on multilayered Fe/Si "lms, which are taken as model systems of the ferromagnetic metal } nonmagnetic interlayer type. Collinear (ferro- magnetic and antiferromagnetic) and noncollinear structures are both possible in these "lms depend- ing on the thickness of the Si and Fe layers. The theoretical studies of magnetization reversal in the ferromagnetic metal } nonmagnetic interlayer sys- tem [1}3] show that the particular type of stable collinear or noncollinear con"gurations is depen- dent on the competition between the bilinear and biquadratic exchanges during the interaction of magnetic layers. The bilinear exchange tends to bring the magnetic layer system into collinear or- dering, while the biquadratic exchange aligns the magnetic moments of adjacent Fe layers in perpen- dicular pairs. The presence of the bilinear and bi- quadratic exchange comparable in value permits a diversity of noncollinear structures in the multi- layered "lms and transformations from one struc- ture to another. In earlier experiments on magnetization reversal in Fe/Si "lms [2,4,5] the formation of stable 0304-8853/00/$ - see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 - 8 8 5 3 ( 0 0 ) 0 0 0 0 2 - 0