Journal of Electron Spectroscopy and Related Phenomena 144–147 (2005) 737–739 Probing the magnetization vectors in layered magnetic structures D.H. Wei a, ∗ , Y.J. Hsu a , Jo-Hsuan Sun a , Chao-Cheng Lin b , Chih-Huang Lai b a National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan b Department of Material Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan Available online 24 February 2005 Abstract Using the X-ray magnetic circular dichroism, we measured the orientations of magnetic moment at exchange-coupled Co/Tb x Fe 1-x bilayers. The moment associated with each element was found tilting an angle with respect to surface normal. Study of the thickness dependence on Co film shows increasing planar component for thicker film. With a fixed 15 ˚ A Co layer deposited on Tb x Fe 1-x , lower Tb percentage leads to larger tilting angle. Element-specific measurements confirm that all three moments have similar orientation at interface, suggesting strong interlayer coupling. © 2005 Elsevier B.V. All rights reserved. Keywords: Magnetic thin film; X-ray magnetic circular dichroism; Exchange-coupling A key ingredient in modern magnetic devices that con- sist of layered structure is the exchange bias (EB), in which the magnetization of a ferromagnetic (FM) layer is unidi- rectionally pinned by its adjacent antiferromagnetic (AFM) layer. This phenomenon is found not only at FM/AFM, but FM/ferimagnet (FI) and FM/FM bilayers as well [1,2]. Be- cause the magnetic anisotropy is originated from the ex- change coupling between two layers with different magnetic orders, it is of great interest to obtain the spin configura- tions at interfacial region as well as the response of each element within one layer due to the presence of the others. In this report, we present an X-ray magnetic circular dichroism (XMCD) study on a system composing a Co layer having in-plane anisotropy deposited on top of a TbFe layer having perpendicular uniaxial anisotropy. The strong coupling be- tween rare-earth transition metal (RE-TM) and FM bilayer makes Co/TbFe a good candidate to study the orientation of magnetic moments through varying the parameters such as film thickness and composition in the layered structure. The samples were prepared by magnetron sputtering at a base pressure of 3 × 10 -7 Torr onto Si substrates. Three sam- ples with 15, 30, and 50 ˚ A thick Co were deposited on top of a 300 ˚ A Tb 21.3 Fe 78.7 layer under a 150 Oe in-plane field ∗ Corresponding author. Tel.: +886 3 5780281; fax: +886 3 5783813. E-mail address: dhw@nsrrc.org.tw (D.H. Wei). to examine the thickness dependence in interlayer coupling. The second series of samples involves tuning the anisotropy in FI layer by varying its composition [3]. With a 15 ˚ A Co top layer, the magnetization of each element was determined for the Tb x Fe 1-x at x = 15.1, 26.6, and 33.6%. All samples described here have a 3-nm aluminium capping layer to pre- vent oxidation during sample transport between chambers. Fig. 1 illustrates the experimental geometry. The elliptically polarized photons irradiate the sample at a 25 ◦ grazing angle. Recording the Co L 2,3 -edge, Fe L 2,3 -edge, and Tb M 4,5 -edge absorption spectra at opposite photon helicity (+σ and -σ ), the XMCD signal is obtained through the absorption asym- metry; [I(+σ ) - I(-σ )]/[I(+σ )+ I(-σ )], where I(σ ) is the ab- sorption intensity measured at characteristic absorption edges under polarization σ . The XMCD signal acquired in such geometry contains contributions from both in-plane (M ‖ σ ‖ ) and out-of-plane (M ⊥ σ ⊥ ) components. To distinguish them, the measurement is repeated after rotating the sample 180 ◦ with respect to the surface normal to take into account that planar compo- nent changes sign while perpendicular component remains unchanged. For magnetization tilting from surface normal at an angle of φ, a simple calculation gives the following rela- tion: φ = tan -1 [(κ - 1)tan θ/(κ + 1)], where θ and κ are photon incident angle (25 ◦ in this study) and the ratio of XMCD sig- nals taken at 0 ◦ and 180 ◦ azimuthal angle, respectively. The 0368-2048/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.elspec.2005.01.026