Spin glass behavior in frustrated quantum spin system CuAl2O4 with a possible orbital liquid state

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Title
Spin glass behavior in frustrated quantum spin system CuAl2O4 with a possible orbital liquid state
Author(s)
Nirmala R.; Kwang-Hyun Jang; Hasung Sim; Hwanbeom Cho; Junghwan Lee; Nam-Geun Yang; Seongsu Lee; R M Ibberson; Kakurai K.; Matsuda M.; Cheong S.-W.; Gapontsev V.V.; Streltsov S.V.; Je-Geun Park
Publication Date
2017-02
Journal
JOURNAL OF PHYSICS-CONDENSED MATTER, v.29, no.13, pp.13LT01 -
Publisher
IOP PUBLISHING LTD
Abstract
CuAl2O4 is a normal spinel oxide having quantum spin, S = 1/2 for Cu2+. It is a rather unique feature that the Cu2+ ions of CuAl2O4 sit at a tetrahedral position, not like the usual octahedral position for many oxides. At low temperatures, it exhibits all the thermodynamic evidence of a quantum spin glass. For example, the polycrystalline CuAl2O4 shows a cusp centered at ∼2 K in the low-field dc magnetization data and a clear frequency dependence in the ac magnetic susceptibility while it displays logarithmic relaxation behavior in a time dependence of the magnetization. At the same time, there is a peak at ∼2.3 K in the heat capacity, which shifts towards a higher temperature with magnetic fields. On the other hand, there is no evidence of new superlattice peaks in the high-resolution neutron powder diffraction data when cooled from 40 to 0.4 K. This implies that there is no long-ranged magnetic order down to 0.4 K, thus confirming a spin glass-like ground state for CuAl2O4. Interestingly, there is no sign of structural distortion either although Cu2+ is a Jahn-Teller active ion. Thus, we claim that an orbital liquid state is the most likely ground state in CuAl2O4. Of further interest, it also exhibits a large frustration parameter, f = |θ CW/T m| ∼ 67, one of the largest values reported for spinel oxides. Our observations suggest that CuAl2O4 should be a rare example of a frustrated quantum spin glass with a good candidate for an orbital liquid state. © 2017 IOP Publishing Ltd
URI
https://pr.ibs.re.kr/handle/8788114/3464
ISSN
0953-8984
Appears in Collections:
Center for Correlated Electron Systems(강상관계 물질 연구단) > Journal Papers (저널논문)
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