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Evolution of spin relaxation processes in LiY1-xHoxF4 studied via ac-susceptibility and muon spin relaxation

Johnson, R. C., Malkin, B. Z., Lord, J. S., Giblin, Sean, Amato, A., Baines, C., Lascialfari, A., Barbara, B. and Graf, M. J. 2012. Evolution of spin relaxation processes in LiY1-xHoxF4 studied via ac-susceptibility and muon spin relaxation. Physical Review B Condensed Matter and Materials Physics 86 (1) , 014427. 10.1103/PhysRevB.86.014427

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Abstract

We present measurements of magnetic field and frequency dependence of the low-temperature (T = 1.8 K) ac-susceptibility and temperature and field dependence of the longitudinal field positive muon spin relaxation (μSR) for LiY1-xHoxF4 with x = 0.0017, 0.0085, 0.0408, and 0.0855. The fits of numerical simulations to the susceptibility data for the x = 0.0017, 0.0085, and 0.0408 show that Ho-Ho cross-relaxation processes become more important at higher concentrations, signaling the crossover from single-ion to correlated behavior. We simulate the muon spin depolarization using the parameters extracted from the susceptibility, and the simulations agree well with our data for samples with x = 0.0017 and 0.0085. The μSR data for samples with x = 0.0408 and 0.0855 at low temperatures (T < 10 K) cannot be described within a single-ion picture of magnetic field fluctuations and give evidence for additional mechanisms of depolarization due to Ho3+ correlations. We also observe an unusual peak in the magnetic field dependence of the muon relaxation rate in the temperature interval 10-20 K that we ascribe to a modification of the Ho3+ fluctuation rate due to a field induced shift of the energy gap between the ground and the first excited doublet crystal field states relative to a peak in the phonon density of states centered near 63 cm-1.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QC Physics
Uncontrolled Keywords: Spin glasses and other random magnets, Muon spin rotation and relaxation, Dynamic properties, Rare-earth ions and impurities
Publisher: American Physical Society
ISSN: 1098-0121
Last Modified: 04 Jun 2017 04:37
URI: http://orca.cf.ac.uk/id/eprint/41522

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