Ⅲ-2. Atomic & Solid State Physics (Muon)

RIKEN Accel. Prog. Rep. 49 (2016)

μSR Result
Result onLa
μSRon Magnetic
Magneticgroundgroundstate
stateofofCeCe
La(T == Ru,Ru, Os)Os)
xT
1-x1-x2Al1010 (TxT
2Al
N. Adam,䠆1,䠆2 H. Tanida,䠆3 D. T. Adroja,䠆4 M. Sera,䠆3 T. Takabatake,䠆3 and I. Watanabe䠆1
Ce-based caged-type compounds, CeT 2Al10 (T= Ru, Os)
have generated great interest due to their Kondo
semiconducting state and an anomalously high magnetic
ordering temperature T0 ~ 30 K with spin gap formation at
low temperatures 1-2). Neutron diffraction studies ofCeT2Al10 for T= Ru and Os revealed small orderedmoments, 0.34 μB and 0.29 μB, along the c-axis
respectively although these two compounds exhibit a large
anisotropy of magnetic susceptibility χa > χc > χb 3,4). This
indicates that the moment direction is governed by theanisotropic magnetic exchange and not by the CEF
anisotropy 5,6).
In order to investigate the relation between the moment
direction and the spin gap energy, magnetic Ce (4f1) issubstituted with nonmagnetic La (4f0), as in Ce1-xLaxT2Al10,
assuming that it would change the magnetic moment due todifferent lattice parameters. However, an unusually orderedstate is realized. In the case of Ce0.9La0.1Os2Al10, neutron
diffraction studies have shown that the ordered moment
remains along the c-axis and the Ce moment reduces withan increasing La concentration without any changes in thespin direction 6). Compared to Ce1-xLaxRu2Al10, the directionof the ordered moment changes from c-axis to b-axis andthe moment is reduced to 0.18 μB after 7% La doping 7).
In order to gain further information on the microscopicchange in magnetism, we performed muon spin relaxation(μSR) on a Ce1-xLaxRu2Al10 (x = 0.05, 0.07, 0.10) andCe1-xLaxOs2Al10 (x = 0.10, 0.24, 0.50) alloy. The μSR
experiments were carried out using the JANIS in
CHRONUS (Port-4) spectrometer in longitudinal geometryat RIKEN-RAL, UK. Fig. 1 (a-d) shows thezero-field (ZF) μSR spectra of Ce1-xLaxRu2Al10 (x = 0.07and 0.10) and Fig. 2 (a-d) shows the ZF- μSR spectra for
Ce1-xLaxOs2Al10 (x = 0.24 and 0.50). The panels on the left
side of the figures show the spectra at low temperatures,
while those on the right side show the spectra at hightemperatures.
As shown in the Figs. 1(a), 1(c), and 2(a), the spectra
exhibit clear signs of oscillation with strong damping
confirming the long range magnetic ordering of the Ce
moment below T0. Meanwhile in Figs. 1(b), 1(d) and 2(b),we can observe the magnetic transition at 24 K, 21 K, and 8K, respectively. On the other hand, the μSR spectra ofCe1-xLaxOs2Al10 (x = 0.5) at 2 K in Fig. 2(c) reveal a
non-magnetic ground state below T0. The same behavior canbe observed in Figs. 1(b), 1(d), 2(b), and 2(d) above the________________________________________________RIKEN Nishina Center
Computational Chemistry and Physics Laboratory, Universiti Sains
Malaysia
䠆3ADSM, Hiroshima University
䠆4
ISIS Facility, Rutherford Appleton Laboratory
䠆1
䠆2- 215 -Fig. 1

ZF-μSR of Ce1-xLaxRu2Al10Fig. 2

ZF-μSR of Ce1-xLaxOs2Al10

magnetic transition temperature which is a typical muon
response to static distribution of the nuclear dipole moment.
References

1) A. M. Strydom, Physica B, 404, 2981 (2009).
2) T. Nishioka et al., JPSJ, 78, 123705 (2009).
3) D. D. Khalyavin et al., Phys. Rev. B 82, 100405(R) (2010).
4) H. Kao et al., J. Phys. Soc. Jpn. 80, 073701 (2011).
5) J.-M. Mignote et al., Phys. Rev. B 89, 161103 (2014).
6) D.T. Adroja et al., Phys. Rev. B 92, 094425 (2015).
7) H. Tanida et al., JPS Conf. Proc. 3, 011073 (2014).