Photon Factory Activity Report 2016 #34 (2017)
BL-16A/2016S2-005, 2014G677

Irradiation Effect on Magnetic Properties of FeRh Thin Films
with Energetic C60 Cluster Ion BeamToshiyuki Matsui1*, Ryunosuke Soma2, Yuichi Saitoh3, Masako Sakamaki4,Kenta Amemiya4, AkihiroIwase2
1
Faculty of Arts and Sciences, Osaka Prefecture University, Sakai, Osaka, Japan2
Department of Materials Science, Osaka Prefecture University, Sakai, Osaka, Japan
3
National Institutes for Quantum and Radiological Science and Technology, Takasaki, Gunma, Japan
4
High Energy Accelerator Research Organization, Tsukuba, Ibaraki, JapanThe abstract is optional; if your report is long and an abstract is necessary, please include it here. If an abstract is notnecessary, please delete this sentence.
1 Introduction
Iron rhodium is known to exhibit a first order magnetic
phase transition from anti-ferromagnetic to ferromagnetic
near room temperature. We have ever revealed thatenergetic ion beam irradiation induces FM state below
room temperature. [1] In addition, the change inmagnetization of ion irradiated FeRh was considered tobe mainly dominated by the deposition energy throughelastic collisions between the ions and the sample species.
[2] In the recent studies, however, the saturation
magnetization of the sample irradiated with the Au3
cluster ion has known to exhibit larger magnetization thanthat of the sample irradiated with the Au single ion, evenwhen the same number of Au ions are irradiated. Here, inorder to clarify such effect, we examined this cluster
effect in the case of C60 cluster ion.
2 ExperimentThin film samples of FeRh with 50 nm thick were
deposited on MgO substrates by ion beam sputtering. Thesamples were irradiated with 83 keV C1 ion beam in thefluence of 6.75x1012/cm2, 1.35x1013/cm2, 1.35x1014/ cm2,
as well as with 5 MeV C60 ion beam in the corresponding
fluence. The magnetic properties were characterized by
X-ray magnetic circular dichroism (XMCD), as well as a
SQUID magnetometer
3 Results and Discussion
Figure 1 shows the XMCD spectra at the Fe L2 andL3-edges for the unirradiated and irradiated samples. As
seen in the figure, XMCD signal for the C60 samples
shows larger XMCD signal than that of the C1 samples.
In contrast, the samples irradiated with considerably large
amount C1 and C60 ions, the opposite tendency can beobserved in Fig. 2 for the same ion fluence. On the otherhand, with larger ion fluence, the spectrum for the sample
irradiated with C1 ion shows larger XMCD signal thanthat for the sample irradiated with C60 cluster ion.
Figure 3 shows that the magnetic moment per Fe atom
as a function of ion fluence, which was obtained byanalyzing XMCD spectra. As can be seen in the figure,for the sample irradiated with C60 cluster ion, themagnetic moment significantly increases with relatively

Fig. 1: XMCD spectra for the irradiated samples with theC1 and C60 cluster ion.

Fig. 2: XMCD spectra for the irradiated samples with theC1 and C60 cluster ion.

Photon Factory Activity Report 2016 #34 (2017)

small ion fluence and then starts to decreases withincrease in the ion fluence. In contrast, as for the sample
irradiated with C1 ions, it monotonically increases withincreasing ion fluence.
These results show that C60 cluster ion irradiation caneffectively induced the ferromagnetic order in the ultrasurface region of the sample rather than C1 single ionirradiation. This is also qualitatively in agreement withthe result in the case of Au cluster ion irradiation. We will
discuss the effect of ion clustering for irradiation induced
ferromagnetic ordering in FeRh.
References[1] M. Fukuzumi et al, Nucl. Instr. and Meth.B, 230, 269(2005).
[2] N. Fujita et al., J. Appl. Phys. 107, 09E302 (2010).
* matsui@las.osakafu-u.ac.jp

Fig. 3: Ion fluence dependence of magnetic moment per
Fe atom for the samples irradiated samples with
C1 and C60 cluster ions. The magnetic moment
was calculated by using sum rule analysis for theXMCD spectra of the samples.