Photon Factory Activity Report 2004 #22 Part B (2005)
Surface and Interface

7A/2003G014

The Spin Reorientation Transitions and Magnetic Anisotropy Energies ofFe/Ni/Cu(001) films studied by depth-resolved XMCD techniqueExperiments
XMCD experiments were performed at BL-7A. Fe andNi films were deposited on a cleaned Cu(001) by anelectron-beam evaporation. The thickness was monitored
by a RHEED observation. To obtain the magnetic
anisotropy phase diagram, wedge-shaped Ni samples
were prepared, which slopes were 1-2 ML/mm. Thesample was magnetized by a pulsed current through a coil.
Circularly polarized(~80%) x-rays were obtained byusing the light emitted downwards from the electron orbitof the storage ring. In order to reveal the depth profiles of
the Ni orbital magnetic moment, depth-resolved XMCD
study [3] was performed in the partial electron yield modeby using a microchannel plate detector. XMCD spectra
were obtained by reversing the film magnetization. The
direction of the magnetization was examined bymeasuring XMCD spectra at normal (90º) and grazing(30º) x-ray incidences, which are referred to “NI” and“GI”, respectively.
Results and discussion
Fig. 1a shows a series of XMCD spectra taken during astepwise Fe deposition on a Ni(7.5 ML)/Cu film. Thespectra show in-plane, perpendicular, and in-planemagnetization as the Fe thickness increases. From a seriesof XMCD measurements for the wedged Ni samples, amagnetic anisotropy phase diagram of Fe/Ni/Cu wasobtained (see Fig. 1b). Note here that in-plane magnetizedNi films (<9 ML) undergo twice spin reorientationtransitions (SRTs). The first one to perpendicular occurs
even with a small amount (<0.5 ML) of Fe deposition. In
contrast, the perpendicularly magnetized Ni/Cu film (< 16ML in the present experiment) shows a SRT to in-planemagnetization by 1-2 ML Fe film deposition.
The depth-resolved XMCD spectra were analyzed toobtain probing depth dependences of the Ni orbital

64

Users' Report

0.4 Fe 0.0 ML
0.0-0.4(a)-0.8
0.4 Fe 0.7 ML
0.0-0.4-0.8
0.4 Fe 4.0 ML
0.0GI-0.4-0.8NI
850 860 870 880
Photon Energy (eV)Fe film thickness (ML)Introduction
It has been reported that the Ni films on Cu(001)exhibit an in-plane magnetization below 8 ML, and aperpendicular one between 9-37 ML [1]. It is also known
that the magnetic anisotropy is sensitive to surface orinterface structures. For instance, H or CO adsorption
stabilizes the perpendicular magnetic anisotropy [2].
In the present study, we investigated Fe/Ni/Cu(001)magnetic films to clarify the magnetic anisotropy and thedepth profiles of the nickel orbital magnetic moment.

XMCD intensity

Hitoshi ABE1, Kenta AMEMIYA*1, Daiju MATSUMURA1, Soichiro KITAGAWA1,22
1Hirokazu WATANABE , Toshihiko YOKOYAMA , and Toshiaki OHTA
1Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
2Institute for Molecular Science, Myodaiji-cho, Okazaki, Aichi 444-8585, Japan
2.0(b)

1.5
1.0
0.5
0.0
68 10 12 14 16
Ni film thickness (ML)

Fig. 1. (a) Ni L-edge XMCD spectra of Fe(xML)/Ni(7.5 ML)/Cu(001). (b) The magneticanisotropy phase diagram of Fe/Ni/Cu(001). The
open circle represents in-plane magnetization, thesolid square perpendicular.
magnetic moment(not shown). The magnetic anisotropy
energy(MAE) should be proportional to the orbital
moment difference between perpendicular and in-planemagnetization[4,5]. Then MAE values can be estimatedby this relationship and the magnetic moment data. The
obtained MAEs of nickel are listed in table 1.
According to table 1, the MAE of the top layer issignificantly reduced upon iron deposition, while that of
the inner layer almost remains.
The MAEs of iron were also estimated to be 210 (< 1ML) and 13 µeV/atom (2 ML). This means that the single
layer iron favours perpendicular magnetization strongly,
while the 2 ML-thick iron does not.
The two boundary lines which can be obtained fromthe data such as the MAEs are depicted in Fig.1b as bluelines. These are in good agreement with the points
experimentally obtained. Thus, the SRTs can beunderstood at the depth-resolved point of view.
Table 1: The magnetic anisotropy energy values of Ni
Bare Ni
Fe covered Ni(µeV/atom)
Top layer-177-36
Inner layer
3334
References[1] W.L. O’Brien et al., Phys. Rev. B 54, 9297 (1996).
[2] D. Matsumura et al., Phys. Rev. B 66, 024402(2002).
[3] K. Amemiya et al., Appl. Phys. Lett. 84, 936 (2004).
* amemiya@chem.s.u-tokyo.ac.jp