JAEA-Review-2010-065.pdf:15.99MB - 日本原子力研究開発機構

Effect of Au Cluster Ion Irradiation on Magnetic
Properties of FeRh Thin Films
A. Iwase a) , N. Fujita a) , S. Kosugi a) , Y. Saitoh b) and T. Matsui a)
a) Department of Materials Science, Osaka Prefecture University,
b) Department of Advanced Radiation Technology, TARRI, JAEA
Recently, we have found that energetic ion irradiation
induces ferromagnetic state in Fe-53at% Rh alloy which
intrinsically shows anti-ferromagnetic state. The
irradiation induced magnetic transition is caused by the
elastic interaction between irradiating ions and FeRh
target 2) . In this report, we show the effect of cluster ion
irradiation on the magnetic state of FeRh thin films.
Fe 47Rh 53 thin films about 40 nm thick were irradiated
with Au 1 ions and Au 3 cluster ions at room temperature by
using a tandem accelerator at JAEA-Takasaki. Ion
energies were 1.67 MeV for Au 1 ions and 5.0 MeV for Au 3
cluster ions. The fluences of Au 1 ions were 3 × 10 11
Au/cm 2 , 1 × 10 12 Au/cm 2 , and 3 × 10 12 Au/cm 2 . The
fluences of Au 3 ions were 1 × 10 11 Au 3/cm 2 , 3.5 ×
10 11 Au 3/cm 2 , and 1 × 10 12 Au 3/cm 2 . Before and after the
irradiations, the magnetic hysteresis (M-H curves) was
measured in a field range of -6 to 6 kOe at 20 K using a
SQUID magnetometer.
Figure 1 shows the M-H curves for FeRh thin films
irradiated with Au 1 ions. The magnetization of the FeRh
films increases with increasing the ion fluence.
Magnetization[emu/cc]
4-42
300
200
100
0
-100
-200
unirrad.
3x10 11 /cm 2
1x10 12 /cm 2
3x10 12 /cm 2
-300
-6000 -4000 -2000 0 2000 4000 6000
Magnetic Field[Oe]
Fig. 1 M-H curves at 20 K for FeRh thin films
irradiated with 1.67 MeV Au 1 ions.
Figure 2 indicates that a same trend can be observed in
the effect of Au 3 cluster ion irradiation on M-H curves.
Figure 3 shows the value of saturation magnetization, Ms,
as a function of the number of incident Au atoms. Even at
the same number of incident Au atoms, the value of Ms for
Au 3 cluster ion irradiation is larger than that for Au 1 ion
irradiation. The present result implies that not only the
total energy deposited through the elastic interaction but also
the spatio-temporal overlapping of the interaction with each
JAEA-Review 2010-065
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constituent atom of the cluster ions is important to
understand the effect of cluster ion irradiation on the
magnetic properties of FeRh alloy.
300
200
100
0
-100
-200
-300
-6000 -4000 -2000 0 2000 4000 6000
Magnetization[emu/cc]
250
200
150
100
50
0
unirrad.
1x10 11 /cm 2
0 5 10 11
3.5x10 11 /cm 2
1x10 12 /cm 2
Au1
Au3
Magnetic Field[Oe]
Fig. 2 M-H curves at 20 K for FeRh thin films
irradiated with 5.0 MeV Au 3 cluster ions.
1 10 12
1.5 10 12
Fig. 3 Values of Ms as a function of the number of
incident Au atoms for Au 1 and Au 3 cluster ion
irradiations.
References
1) N. Fujita et al., Nucl Instrum. Meth. Phys. Res. B 267
(2009) 921-924.
2) N. Fujita et al., J. Appl. Phys. 107 (2010) 09 E 302.
3) N. Fujita et al., Jpn. J. Appl. Phys. 49 (2010) in press.
2 10 12
2.5 10 12
Number of incident Au atoms(1/cm 2 )
3 10 12
3.5 10 12