Moessbauer and resistivity studies of the magnetic and electronic properties of the high-pressure phase of Fe{sub 3}O{sub 4}
- 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, Vol. 70, Issue 17; Other Information: DOI: 10.1103/PhysRevB.70.174106; (c) 2004 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
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