RIKEN Accel. Prog. Rep. 50 (2017)

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

Investigation on spin dynamics of a staircase kagome material by using spinpolarized muons
㻖3 䠆3
㻖3 䠆3
㻖2
㻖1,㻖2 䠆1,䠆2
䠆2
S. Yoon,Do,Do
K.-Y.
Choi,B.
Suh,andWatanabe
SungwonYoon㻖1,,䠆㻖21,S.-H.
S.-H.
, K.-Y.
Choi, J.B.
J. Suh,䠆2 I.and
I. Watanabe

PbCu3TeO7 was suggested as a Cu-based anisotropic
kagome material with the staircase kagome lattice.1) The
crystal structure of PbCu3TeO7 is an orthorhombic latticewith the space group, Pnma, No. 62.2) PbCu3TeO7 is formed
by a buckled kagome layer, and each layer is alternativelyarranged Cu2+ ions in the different environments ofsurrounding O2- ions, the octahedral, and the tetrahedral
crystal environments, respectively.1), 2) Since all buckled
kagome layers are not only stacked along the a axis, butalso separated by Pb, and Te atoms, they can be in a twodimensional network of Cu2+ ions. Therefore, it is expectedthat several magnetic anomalies emerge for different crystalenvironments.1)
We synthesized a PbCu3TeO7 polycrystalline sample, andwe found several magnetic anomalies from the DC
magnetic susceptibility and the specific heat results. TheDC susceptibility exhibits three distinct anomalies at 17 K,
25 K, and 36 K, and the Weiss temperature is extracted
approximately 180 K by the Curie Weiss law, indicating ahighly frustrated spin state. The specific heat result also
indicates that the magnetic entropy over 36 K remains
around 50 %. The experimental results of the nuclear
magnetic resonance also support a frustrated spin state.3)
With the consideration of previous experimental results, it
can be suggested that PbCu3TeO7 is in the frustrated spinstate with several magnetic anomalies, as revealed inanisotropic kagome materials. 1) However, it is unrevealed
the nature of magnetic anomalies in the Cu-based staircase
kagome material.

In order to understand the nature of the magnetic
anomalies, we conduct a microscopic investigation using
spin-polarized muons at the RIKEN-RAL Muon Facility.
Because the muon is highly sensitive of the small magneticfield, the muon is expected to provide a clue for thecharacteristics of magnetic anomalies.
In Fig. 1, it shows the temperature dependence of theinternal field around 36 K obtained from the muonpolarization at zero field by fitting with the oscillation
function to represent the magnetic ordered state. Thisanomaly can be described by the two-dimensional Ising
spin state with aphenomenological function to express themagnetic ordered state in the range from 32 K to 36 K. It issuggested that the anomaly at 36 K is induced by the twodimensional network including Cu2+ ions in the tetrahedral
environment.

Fig. 2. Temperature dependence of the slow relaxing
component obtained by the muon polarization at alongitudinal field (LF) of 10 G, and the inset of revealing
several spectra of the muon polarization at LF = 10 G.

Fig. 1. Temperature dependence of the internal fieldobtained by the muon polarization at zero field with a fit
obtained using the phenomenological equation of themagnetic ordered state, and the inset of exhibiting several
time differential spectra of the muon polarization at zerofield.
䠆1

RIKEN Nishina Center
Department of Physics, The Catholic University of Korea
䠆3
Department of Physics, Chung-Ang University
䠆2

Exhibited in Fig. 2, it was extracted the temperaturedependence of the relaxation rate from the relaxation
component on a latter time region of the muon polarization
at a weak longitudinal field for the exclusion of thecontribution of the nuclear dipole moment. It supports thatthe behavior of the ordered state at 36 K is close to thesecond-order phase transition. Furthermore, a slightincrease of the relaxation rate below 5 K was found,suggesting a frustrated spin state.
References
1) B. Koteswararao et al., J. Phys.: Condens. Matter 25, 336003(2013).
2) B. Wedel and H. Mueller-Buschbaum, Z. Naturf. B 51, 1587
(1996).
3) DAI Jia et al., Chin. Phys. Lett. 32, 127503 (2015).

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