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

7A/2004G

Depth-resolved estimation of MAEs of 2 ML Fe on Ni/Cu(001) films
Hitoshi ABE1, Kenta AMEMIYA*1, Daiju MATSUMURA1,2, Takumi Otsuki1, Enju SAKAI1,Toshihiko YOKOYAMA3, and Toshiaki OHTA1,4
1
Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Jap
2Japan Atomic Energy Agency, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan
3
Institute for Molecular Science, Myodaiji-cho, Okazaki, Aichi 444-8585, Japan4
SR Center, Ritsumeikan University, Noji-Higashi, Kusatsu, Shiga 525-8577, JapanExperiment
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. Perpendicularly magnetizedFe(2 ML)/Ni(22 ML)/Cu(001) and in-plane magnetizedFe(2 ML)/Ni(8 ML/Cu(001) films were prepared in orderto reveal the MAEs of 2 ML iron on Ni films.
The sample was magnetized by a pulsed current
through a coil. Circularly polarized (~80%) x-rays wereobtained by using the light emitted downwards from theelectron orbit of the storage ring. In order to reveal thedepth profiles of the Fe orbital to spin magnetic moment
ratios, depth-resolved XMCD experiment [3] wasperformed in the partial electron yield mode by using a
microchannel plate detector. XMCD spectra wereobtained 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
Obtained depth–resolved XMCD spectra were analyzed
to estimate orbital to spin magnetic moment ratios of ironwith the sum rules [4,5]. Figure 1a shows probing depth

dependences of iron orbital to spin magnetic mom
ratios of the Fe(2 ML)/Ni(22 ML)/Cu(001) film, w
was magnetized perpendicular to the sample planemeasured in NI geometry. The moment ratios ofML)/
ML)/Cu(001)(a)
0.0975are shown in Fig
where the film
0.0970magnetized in-p0.0965
and measured ingeometry.
10 12 14 16 18 20 22
The plot in Fig
increases
but tha(b)0.0940Fig. 1b decre0.0935
with decreasingprobing depths.
0.0930moment ratio of
top layer was la
10 11 12 13 14 15
Probing depth (Angstrom)
than the bottom lFig. 1
Probing depth
when the film
dependence of ml/ms of 2 ML
perpendic
Fe on Ni(22 ML)/Cu(001) (a)magnetization,and Ni(8 ML)/Cu(001) (b).
smaller with in-p
magnetization. Fitting the plots with a simple model
moment ratios of the top and bottom layers were obta
These moment ratios were 0.114 and 0.077
perpendicularly magnetized 2 ML Fe (Fig. 1a), and 0and 0.116 for in-plane magnetized one (Fig. 1b).
These values give us the results of Ktop = 174 and K-168 µeV/atom according to Bruno’s model [6]. Tvalues mean that the top layer has a large perpendic
anisotropy and the bottom layer a large in-plane one.
sum of these two is 6 µeV/atom, indicating
anisotropy as a whole film, which is in good agreem
with the MAE of 9 µeV/atom obtained from total elec
yield measurements.

Moment ratio ml / msIntroductionIt 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 has been also
revealed [2] that upon Fe deposition, in-plane magnetizedNi films (≤ 9 ML) undergo the SRT twice; a smalldeposition (< 1 ML) of Fe causes a transition toperpendicular magnetization, and further Fe deposition(1–2 ML in total) causes a return to in-plane.
Perpendicularly magnetized Ni films (≥ 10 ML) also
exhibit a transition to in-plane. The magnetic anisotropyenergies (MAEs) of Fe in the system have been estimatedto be 140 (< 1 ML) and 9 µeV/atom (2 ML). The single
layer iron favours perpendicular magnetization strongly,
while the 2 ML-thick Fe does not.
In the present study, 2 ML Fe deposited on Ni/Cu(001)films was investigated to clarify the MAEs of the top(Ktop) and bottom (Kbot) layers by using the depth-resolved
XMCD technique [3].

References[1] W. L. O’Brien et al., Phys. Rev. B 54, 9297 (1996)[2] H. Abe et al., J. Magn. Magn. Mater. 302, 86 (200[3] K. Amemiya et al., Appl. Phys. Lett. 84, 936 (2004[4] B.T. Thole et al., Phys. Rev. Lett. 68, 1943 (1992)[5] P. Carra et al., Phys. Rev. Lett. 70, 694 (1993)[6] P. Bruno, Phys. Rev. B 39, R865 (1989)* amemiya@chem.s.u-tokyo.ac.jp

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