Low-temperature spin dynamics of a valence bond glass in Ba2YMoO6
Autor: | J. O. Piatek, Henrik M. Rønnow, James S. Lord, Martin Míšek, Jan-Willem G. Bos, M. A. de Vries |
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Jazyk: | angličtina |
Rok vydání: | 2013 |
Předmět: |
Muon
Materials science Strongly Correlated Electrons (cond-mat.str-el) Condensed matter physics Magnetic moment MPBH FOS: Physical sciences General Physics and Astronomy Disordered Systems and Neural Networks (cond-mat.dis-nn) 02 engineering and technology Electron Muon spin spectroscopy Condensed Matter - Disordered Systems and Neural Networks 021001 nanoscience & nanotechnology 01 natural sciences Magnetic susceptibility Condensed Matter - Strongly Correlated Electrons Unpaired electron 0103 physical sciences Valence bond theory Condensed Matter::Strongly Correlated Electrons 010306 general physics 0210 nano-technology Ground state |
Zdroj: | NEW JOURNAL OF PHYSICS |
Popis: | We carried out AC magnetic susceptibility measurements and muon spin relaxation spectroscopy on the cubic double perovskite Ba2YMoO6, down to 50 mK. Below ~1 K the muon relaxation is typical of a magnetic insulator with a spin-liquid type ground state, i.e. without broken symmetries or frozen moments. However, the AC susceptibility revealed a dilute-spin-glass like transition below ~ 1 K. Antiferromagnetically coupled Mo5+ 4d1 electrons in triply degenerate t2g orbitals are in this material arranged in a geometrically frustrated fcc lattice. Bulk magnetic susceptibility data has previously been interpreted in terms of a freezing to a heterogeneous state with non-magnetic sites where 4d^1 electrons have paired in spin-singlets dimers, and residual unpaired Mo5+ 4d1 electrons. Based on the magnetic heat capacity data it has been suggested that this heterogeneity is the result of kinetic constraints intrinsic to the physics of the pure system (possibly due to topological overprotection), leading to a self-induced glass of valence bonds between neighbouring 4d1 electrons. The muSR relaxation unambiguously points to a static heterogeneous state with a static arrangement of unpaired electrons isolated by spin-singlet (valence bond) dimers between the majority of Mo5+ 4d electrons. The AC susceptibility data indicate that the residual magnetic moments freeze into a dilute-spin-glass-like state. This is in apparent contradiction with the muon-spin decoupling at 50 mK in fields up to 200 mT, which indicates that, remarkably, the time scale of the field fluctuations from the residual moments is ~ 5 ns. Comparable behaviour has been observed in other geometrically frustrated magnets with spin-liquid-like behaviour and the implications of our observations on Ba2YMoO6 are discussed in this context. 11 pages, 3 Figures. Published in New Journal of Physics |
Databáze: | OpenAIRE |
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