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

J Phys Condens Matter

Center for Strongly Correlated Materials Research, Seoul National University, Seoul 08826, Korea. Department of Physics, Indian Institute of Technology Madras, Chennai 600 036, India. Department of Physics, Sungkyunkwan University, Suwon 16419, Korea.

Published: April 2017

CuAlO is a normal spinel oxide having quantum spin, S  =  1/2 for Cu. It is a rather unique feature that the Cu ions of CuAlO 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 CuAlO 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 CuAlO. Interestingly, there is no sign of structural distortion either although Cu is a Jahn-Teller active ion. Thus, we claim that an orbital liquid state is the most likely ground state in CuAlO. Of further interest, it also exhibits a large frustration parameter, f  =  |θ /T | ~ 67, one of the largest values reported for spinel oxides. Our observations suggest that CuAlO should be a rare example of a frustrated quantum spin glass with a good candidate for an orbital liquid state.

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Source
http://dx.doi.org/10.1088/1361-648X/aa5c72DOI Listing

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