Europhys. Lett.
Volume 65, Number 1, January 2004
Page(s) 123 - 129
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 01 December 2003
Europhys. Lett., 65 (1) , pp. 123-129 (2004)
DOI: 10.1209/epl/i2003-10063-9

Orange peel coupling in multilayers with perpendicular magnetic anisotropy: Application to $\chem{(Co/Pt)}$-based exchange-biased spin-valves

J. Moritz, F. Garcia, J. C. Toussaint, B. Dieny and J. P. Nozières

SPINTEC, CEA/Grenoble/DRFMC - 38054 Grenoble Cedex 9, France

(Received 28 January 2003; accepted in final form 4 November 2003)

Néel's theory of magnetostatic coupling between two magnetic layers with in-plane magnetization separated by a non-magnetic spacer has been extended to the case of multilayers with perpendicular anisotropy. It is shown that the presence of a correlated roughness between the successive interfaces induces an interlayer coupling through the spacer analogous to the well-known orange peel coupling. However, depending on the parameters describing the interfacial roughness, the magnetic anisotropy and the exchange stiffness constant, this coupling can favor either parallel or an antiparallel alignment of the magnetization in the two ferromagnetic layers. This model was used to quantitatively interpret the variation of interlayer coupling vs. thickness of $\chem{Pt}$ spacer layer in out-of-plane magnetized exchange-biased spin-valves comprising ( $\chem{Pt/Co}$) multilayers as free and pinned layers. It is shown that the net coupling can be interpreted by the coexistence of perpendicular orange peel and oscillatory RKKY couplings. Interestingly, since these two couplings have different thickness dependence, in certain range of $\chem{Pt}$ thickness, the coupling changes sign during growth, being antiferromagnetic at the early stage of the growth of the top ( $\chem{Co/Pt}$) multilayer but ferromagnetic once the growth is completed.

75.70.-i - Magnetic properties of thin films, surfaces, and interfaces.
75.30.Gw - Magnetic anisotropy.
75.50.Ss - Magnetic recording materials.

© EDP Sciences 2004