On tilted magnetization in thin films

• Published in: Journal of magnetism and magnetic materials Vol. 183; no. 3; pp. 283 - 291
• Main Authors: UDVARDI, L, KIRALY, R, SZUNYOGH, L, DENAT, F, TAYLOR, M. B, GYÖRFFY, B. L, UJFALUSSY, B, UIBERACKER, C
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Science 01.03.1998
• Subjects: Applied sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Crystal-field theory and spin hamiltonians; Exact sciences and technology; General theory and models of magnetic ordering; Interfacial magnetic properties (multilayers, magnetic quantum wells, superlattices, magnetic heterostructures); Magnetic properties and materials; Magnetic properties of surface, thin films and multilayers; Metals. Metallurgy; Physics; Thin films; Multilayers; Gold; Magnetization; Transition elements; Magnetic anisotropy; Spin Hamiltonians; Theoretical study; Cobalt; Exchange interactions; Bilayers
• ISSN: 0304-8853
• DOI: 10.1016/S0304-8853(97)01084-6

We suggest a new mechanism for explaining the tilt of the magnetization away from the surface normal in certain magnetic ultra-thin films. Our arguments are based on a simple classical spin Hamiltonian in which the magneto-crystalline surface anisotropy is described by H sub a =- Sigma sub i lambda sub i (S sub i exp z ) exp 2 + Sigma sub i gamma sub i (S sub i exp z ) exp 4 , where lambda sub i and gamma sub i are non-negative phenomenological constants, s sub i exp z denotes the z-component (normal to the surface) of the spin at the site labelled by i. In this paper we study only the ground state. In contrast to the usual explanation which attributes the experimentally observed tilted magnetization to the fourth-order term involving gamma sub i , we show that the second-order term alone can lead to this interesting phenomenon. Our explanation implies that the magnetization of the successive layers are not collinear. As an illustration of our arguments we discuss the experimentally observed orientational transition of the Co/Au(111) system in quantitative details.