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

7A, 11A/2005G098

Element specific magnetic hysteresis on Fe/Co/Cu(001)
Takumi OHTSUKI1, Kenta AMEMIYA1,2*, Daiju MATSUMURA1,3, Jun MIYAWAKI1, Hitoshi ABE1,Enju SAKAI1, and Toshiaki OHTA1,4
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, Japan
3
Japan Atomic Energy Agency, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan
4SR Center, Ritsumeikan University, Noji-Higashi, Kusatsu, Shiga 525-8577, Japanthat of Co (Fig.2). This means Fe magnetization near thesurface and interface are antiparallel to each other.
Therefore, the model of reversal process is thought to be
as Fig.1. The magnetizations of each layer are directed inplane and turn by ~120º per layer. First, Fe interface
component rotates with Co, and then the Fe surface andinner layer components rotate slowly (3 to 4 process).
In other thicknesses than 5 and 6 ML, the Fe surface
and interface components showed a parallel coupling.
Therefore, only when the Fe thickness is in region 2 andthe Fe surface and interface magnetization components
are antiparallel to each other, the difference is observed
between the Fe and Co hysteresis curves.

Intensity (arb. units)

1.5FeCo

4

1.0
0.5

3Fe
0.0-0.5

Co-1.0

2

1-1.5
-150

-100

-50

050

100

150

Magnetic Field (Oe)Figure 1. ESMH on Fe(6 ML)/Co(2 ML)/Cu(001)1.0Intensity (arb. units)

Introduction
Magnetic properties of Fe/Co/Cu(001) [1] are divided
into three regions depending on Fe thickness. In region 1(0-4 ML) and 3 (>12 ML), Fe shows homogeneously
magnetized ferromagnetism. However, in region 2 (5-11ML), the Fe surface and interface with Co are
ferromagnetic but the inner layers are antiferromagnetic(TN ~ 200K). The Co layer is homogeneously magnetizedindependent of Fe thickness. The aim of this research is tounderstand the magnetization reversal process of Fe andCo respectively by element specific magnetic hysteresis(ESMH) making use of XMCD.
Experiments
The experiments were performed at BL-7A and 11A.
Co and Fe thin films were evaporated on a clean Cu(001)surface and the thickness was monitored by RHEED.
ESMH was measured as follows: The photon energy wasfixed at the L3 absorption edge of the target element (thehelicity was also fixed) and the sample current wasmeasured with sweeping magnetic field. The samemeasurement was performed at the post-edge energy.
Then ESMH was obtained as the ratio of the former to thelatter. The sample was surrounded by a tungsten meshwith a 900 V bias voltage, which could capture thesecondary electrons and improve the S/N ratio. XMCD
spectra were measured at remanent magnetization by
reversing sample magnetization. In addition, toinvestigate the magnetic depth profile, the depth-resolved
XMCD method [2] was also utilized. The incident angleof X-ray was 20 or 30º from the sample surface.
Results and Discussions
The three Fe regions in Fe(x ML)/Co(3 ML)/Cu(001)were confirmed by XMCD measurements and analyses
with the sum rule. When the Fe thicknesses were inregion 1 or 3, Fe and Co hysteresis overlapped well witheach other. This means Fe and Co magnetic moments
rotate coherently because two elements arehomogeneously magnetized and ferromagneticallycoupled at the interface.
On the other hand, two cases were observed in region 2.
At 5 or 6 ML Fe thickness, a difference was observed
between the Fe and Co hysteresis curves (Fig.1), while
the two loops overlapped at other thicknesses. The depthresolved XMCD result on Fe(6 ML)/Co(2 ML) showsthat XMCD signal of Fe near the surface is opposite toFe (surface)×2

Co (interface)

0.5

0.0

-0.5

-1.0

-1.5
660

690

720

780

810

840

Photon ener gy (eV)Figure 2. XMCD spectrum of Fe(6 ML)/Co(2ML)/Cu(001) obtained by the depth-resolved method
References[1] X.Gao et al., J. Appl. Phys. 97, 103527 (2005).
[2] K.Amemiya et al., Appl. Phys. Lett. 84, 93 (2004).
*kenta.amemiya@kek.jp

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