Photon Factory Activity Report 2005 #23Part B (2006)
Surface and Interface

7A, 11B/2004G325

Surface and interface magnetic anisotropy of Co/Pd (111)
Enju SAKAI1, Kenta AMEMIYA*1,2, Jun MIYAWAKI1, Hitoshi ABE1, Takumi OTUKI1, Toshiaki
OHTA1,3
1
Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
2
Institute of Materials Structure Science, High Energy Accelerator Research Organization, Oho,Ibaraki 305-0801, Japan3
SR Center, Ritsumeikan University, Noji-Higashi, Kusatsu, Shiga 525-8577, Japan
Introduction
The surface and interface properties of magnetic thinfilms are thought to be important factor of theirmagnetism since, compared to a bulk sample, they havelarge proportion in a film. In Co/Pd system, many studies
suggest that interface layer favors perpendicular magnetic
anisotropy (PMA) and cause PMA of a whole film. But
few studies perform direct observation of the interface.
We have investigated the depth-resolved X-ray
magnetic circular dichroism (XMCD) [1]. Surface,interface and inner layer components of XMCD signals
were separately extracted.
Experiment
The experiments were carried out at BL-7A and 11A.
Co was deposited on a clean and ordered Pd(111) surface
at room temperature by electron bombardment heating ofa Co rod. Pd was deposited on the Co film in the same
way and Pd/Co/Pd sandwich film was prepared. The film
thickness is evaluated from spectrum edge jump.
From depth-resolved XMCD experiments, several
spectra with different probing depths are obtained.
Spectral components of the surface layer and rest innerlayers are extracted from the obtained data. A Pd/Co/Pdfilm was used to extract interface spectrum. Further
information on the method is described elsewhere [1].
Results and discussion
Surface and interface orbital magnetic moments areestimated from the extracted spectra by using the sum
rule [2]. Since the orbital magnetic moment is considered
to be the origin of magnetic anisotropy, it can be used in
discussion as shown below.
The estimated orbital moments are shown in Fig.1. In
the all thicknesses, the surface layer has large orbital
moment compared to the inner layers. Since theirdifferences are larger in films with in-plane magnetization,
the surface layer favors in-plane magnetization.
Results of the interface layer are clearer. In PMA
samples, the interface moment is larger than inner layer
one, and an opposite inclination is fond in the case of inplane magnetization. Interface layer thus favors
perpendicular magnetization. 3ML sample is notconsistent with the others, but in such a thin film, theinterface between Co film and substrate cannot be ignored
and the assumption used in this study is not appropriate.

68

Users' Report

Conclusion
Surface and interface magnetic orbital moment ofCo/Pd films and Pd/Co/Pd films are estimated with depthresolved XMCD. The surface favors in-planemagnetization, while the interface favors perpendicularmagnetization. These cause PMA in the thin film region.

Figure.1 Orbital magnetic moment of thesurface and interface layer compared torespective inner layers.
References[1] K. Amemiya et al, Appl. Phys. Lett. 84 936 (2004)[2] B.T. Thole et al, Phys. Rev. Lett. 68, 1943 (1992).
* kenta.amemiya@kek.jp