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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
materials science
Pressure-induced suppression of charge order and nanosecond valence dynamics in Fe
2
OBO
3
Physical Review B - Condensed Matter and Materials Physics, Volume 86, No. 19, Article 195134, Year 2012
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Description
Valence order and fluctuations in the mixed-valence warwickite Fe 2OBO3 have been explored by 57Fe Mössbauer effect spectroscopy at pressures up to 30 GPa in diamond anvil cell experiments. At room temperature a drastic disruption of charge order is evident at ∼11 GPa. There is coexistence of charge order and a progressively increasing abundance of fluctuating valence states in the range extending to ∼16 GPa. At P16 GPa only signatures of electron exchange relaxation, Fe2+ Fe3 +, where represents the resonating mobile carrier, are discerned. Spectral signatures indicate that electron hopping is on a timescale of ∼50 ns, that is, in a time window to which the nuclear resonance technique is particularly sensitive. Low-temperature quenching (∼110 K) at these high pressures (i) is not sufficient to inhibit electron exchange for charge order to reemerge and (ii) reveals that magnetic ordering typical of the charge-ordered phase at low pressure is completely altered to entail new spin dynamics. This evidences the strong interplay between charge order and magnetism and establishes P∼16 GPa as a new electronic phase transition boundary for this system. Nanosecond valence fluctuation signatures persist upon further pressurization to ∼30 GPa at 300 K, suggestive of continued confinement of the mobile carrier to the Fe2+ Fe3+ pair at these extremes. © 2012 American Physical Society.
Authors & Co-Authors
Hearne, Giovanni R.
South Africa, Johannesburg
University of Johannesburg
Sibanda, Wilbert
South Africa, Johannesburg
University of Johannesburg
Carleschi, Emanuela
South Africa, Johannesburg
University of Johannesburg
Pischedda, Vittoria
France, Villeurbanne
Université Claude Bernard Lyon 1
Attfield, John Paul
United Kingdom, Edinburgh
The University of Edinburgh
Statistics
Citations: 11
Authors: 5
Affiliations: 3
Identifiers
Doi:
10.1103/PhysRevB.86.195134
ISSN:
10980121
e-ISSN:
1550235X
Research Areas
Cancer