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

RIKEN Accel. Prog. Rep. 48 (2015)

Muon sites in Ce(Ru, Rh)2Al10 investigated using Density Functional Theory
from the perspective of electronic potential†
N. Adam,＊1,＊2 E. Suprayoga,＊1,＊3 B. Adiperdana,＊4 H. Guo,＊5 H. Tanida,＊6 S.S Mohd-Tajudin,＊2 R. Kobayashi,＊7,＊8M.Sera,＊6 T. Nishioka,＊9 M. Matsumura,＊9 S. Sulaiman,＊2 M.I Mohamed-Ibrahim,＊2 and I. Watanabe＊1,＊2, ＊3, ＊4, ＊5CeRu2Al10 has the orthorhombic YbFe2Al10-type structurewith space group Cmcm.1) Ce atoms control the magnetismof this system and are surrounded by Al atoms forminga cage-like structure which is suggested to form a twodimensional plane structure stacking along the b-axis.2,3)
Despite having the nearest neighbour distance,
approximately 5.2Å between Ce ions, CeRu2Al10 exhibits anantiferromagnetic transition at T0 = 27.3 K which cannot be
explained by taking only RKKY interaction into account. 4)
The magnetic susceptibility is largely anisotropic whereas
the direction of magnetic moment is along the c-axis and is
expected to flip to the a-axis when a small concentration ofRu atoms are substituted by Rh atoms.5) In addition, fromthe µSR results of a Rh-doped system, Guo et al. reported
drastic changes in internal fields at muon sites whichwere related to the spin-flop caused by doping of 3% Rh
atoms in CeRu2Al10.6)
A number of investigations of muon sites in Ce-based
Kondo semiconductors, CeRu2Al10 and Ce(Ru, Rh)2Al10
were carried out by using Density Functional Theory (DFT)
to understand the magnetic properties. From the calculationof electrostatic potential, we found all muon sites previously
suggested by Kambe et al.7) and Khalyavin et al.8) as shownin Figure 1. Because they were not crystallographically
identical, muon sites in CeRu2Al10 are still undefined andthe hyperfine interactions cannot be discussed in detail.

Fig. 1. Muon sites in CeRu2Al10 suggested by Kambe etal.7) and Khalyavin et al. 8)†Condensed from the article in J. Phys.: Conf. Ser. 551 012053 (2014)
RIKEN Nishina Center＊2
Computational Chemistry and Physics Laboratory, Universiti SainsMalaysia＊3Physics Department, Institut Teknologi Bandung＊4Physics Department, Universitas Padjajaran＊5Department of Physics and State Key Laboratory of Silicon Material,Zhejiang University＊6Department of Quantum Matter, Hiroshima University＊7
Quantum Condensed Matter Division, Oak Ridge National Laboratory＊8
Neutron Science Laboratory, University of Tokyo＊9Graduate School of Integrated Arts and Science, Kochi University＊1

Fig. 2. Three planes that differentiate CeRu2Al10 (a) andCe(Ru, Rh)2Al10 (b). Planes (1) and (3) contain the muonsites suggested by Kambe et al., whereas the plane (2)contains the muon sites suggested by Khalyavin et al. In
plane (3), one Ru atom is substituted by one Rh atom.

Fig. 3. Potential differences between non-doped and doped
systems in planes (1), (2) and (3). The purple and yellow
points on the planes indicate the positions of suggested
muon sites.

The potential energies calculated for the plane in the nondoped system were subtracted from those of corresponding
plane in the doped system to investigate the potential
differences. Large differences are seen in plane (3) where aRu atom was substituted by a Rh atom. Because of thischange at the Rh atom in plane (3), the potential energy inplane (2) is also slightly deformed around the position
underneath the Rh atom. The large potential difference atthe substituted Rh atom in plane (3) may have been becauseof the difference in valence configuration from that of Ru
atom.
However, the potential energy at the suggested muonsites did not exhibit much difference even though the Rh
doping concentration in the CeRu2Al10 was increased to12.5%.
References

1) V. M. Thiede et al.: J. Mater. Chem. 8, 125 (1998).
2) H. Tanida et al.: Phys. Rev. B 84, 115128 (2011).
3) M. Sera et al.: J. Phys. Soc. Jpn. 82, 024603 (2013).
4) T. Nishioka et al.: J. Phys. Soc. Jpn. 78 123705 (2009).
5) A. Kondo et al.: J. Phys. Soc. Jpn. 82 054709 (2013).
6) H. Guo et al.: Phys. Rev. B 88 115206 (2013).
7) S. Kambe et al.: J. Phys. Soc. Jpn. 79, 053708 (2010).
8) D. D. Khalyavin et al.: Phys. Rev. B 82 100405 (2010).
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