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Electronic, Magnetic and Structural Properties of the RFeO3 Antiferromagnetic-Perovskites at Very High Pressures

Published online by Cambridge University Press:  01 February 2011

Moshe P. Pasternak ,
W. M. Xu ,
G. Kh. Rozenberg  and
R. D. Taylor
Moshe P. Pasternak
Affiliation:
School of Physics and Astronomy, Tel Aviv University, Tel Aviv, ISRAEL
W. M. Xu
Affiliation:
School of Physics and Astronomy, Tel Aviv University, Tel Aviv, ISRAEL
G. Kh. Rozenberg
Affiliation:
School of Physics and Astronomy, Tel Aviv University, Tel Aviv, ISRAEL
R. D. Taylor
Affiliation:
MST-10, Los Alamos National Laboratory, Los Alamos, NM 87545, U.S.A.
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Abstract

At ambient pressure the orthorhombic perovskites R-orthoferrites (R Ξ Lu, Eu, Y, Pr, and La) exhibit very large optical gaps. These large- gap Mott insulators in which the 3d5 high-spin ferric ions carry large local moments and magnetically order at TN > 600 K, undergo a sluggish structural first-order phase transition in the 30-50 GPa range, with the exception of the LuFeO3 which undergoes an isostructural volume reduction resulting from a high to low-spin crossover. High-pressure methods to 170 GPa using Mossbauer spectroscopy, resistance, and synchrotronbased XRD in diamond anvil cells were applied. Following the quasi-isostructural volume reduction (3-5%) the new phase the magnetic-ordering temperature is drastically reduced, to ∼ 100 K, the direct and super-exchange interactions are drastically weakened, and the charge-transfer gap is substantially reduced. The high-pressure (HP) phases of the La and Pr oxides, at their inception, are composed of high- and low-spin Fe3+ magnetic sublattices, the abundance of the latter increasing with pressure but HP phases of the Eu, Y, and Lu oxides consist solely of low-spin Fe3+. Resistance and Mössbauer studies in La and Pr orthoferrites reveal the onset of a metallic state with moments starting at P > 120 GPa. Based on the magnetic and electrical data of the latter species, a Mott phase diagram was established.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 718: Symposium D – Perovskite Materials , 2002 , D2.7
Copyright
Copyright © Materials Research Society 2002

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