Moessbauer and resistivity studies of the magnetic and electronic properties of the high-pressure phase of Fe{sub 3}O{sub 4}

Journal Article · Mon Nov 01 04:00:00 EST 2004 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PhysRevB.70.174106· OSTI ID:20664941

Xu, W M; Machavariani, G Yu; Rozenberg, G Kh; Pasternak, M P ^[1]

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1. School of Physics and Astronomy, Tel-Aviv University, 69978, Tel Aviv (Israel)

The high-pressure phase of magnetite, h-Fe{sub 3}O{sub 4}, has been studied by Moessbauer spectroscopy, and electrical conductivity to pressure of 140 GPa and in the 5-573 K temperature range. Moessbauer studies following annealing at 573 K and 34 GPa reveal three equal-abundant iron species within two magnetic sublattices, I and II: Fe{sup 3+}(I) sublattice with hyperfine field typical of six-coordinated ferric ions and magnetic ordering temperature T{sub M}(I)>600 K at 34 GPa and a combined Fe{sup 3+}(II) and Fe{sup 2+} species forming a magnetic sublattice II with T{sub M}(II){approx}300 K at 34 GPa. Starting at 50 GPa the Fe{sup 3+}(I) moment gradually collapses becoming nonmagnetic at P>80 GPa. This moment collapse is explained in terms of a charge-transfer d-p gap closure mechanism. T{sub M}(II) decreases with pressure, and to 120 GPa, the highest pressure reached with Moessbauer spectroscopy, Fe{sup 3+}(II) remains magnetically ordered. Resistance studies with a nonannealed and highly stoichiometric sample at 300 K reveal a sharp increase in R at the onset of the h-Fe{sub 3}O{sub 4} phase (P>25 GPa), reaching a 25-fold maximum at {approx}45 GPa, after which it shows a precipitous decrease in the 45-70 GPa range after which it decreases gradually with pressure reaching 10-fold reduction at 140 GPa. The sharp increase in R is attributed to a gap opening once h-Fe{sub 3}O{sub 4} is formed. Starting at P>50 GPa, coinciding with partial correlation breakdown of the Fe{sup 3+}(I) sublattice, a sluggish onset of metallization is observed manifested by a positive dR/dT.

• OSTI ID: 20664941
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 17 Vol. 70; ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANNEALING
CHARGE EXCHANGE
ELECTRIC CONDUCTIVITY
IRON IONS
IRON OXIDES
MAGNETITE
MOESSBAUER EFFECT
PHASE TRANSFORMATIONS
PRESSURE RANGE GIGA PA
STOICHIOMETRY
TEMPERATURE RANGE 0000-0013 K
TEMPERATURE RANGE 0013-0065 K
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K