Effect of iron substitution on the structural, electric, and magnetic properties in R-type PbFe{sub x}V{sub 6-x}O{sub 11}, a frustrated system
- Universite des Sciences et Technologies de Lille, Villeneuve (France)
- Univ. of Texas, Austin, TX (United States)
Single-phase material of the solid solution PbFe{sub x}V{sub 6-x}O{sub 11} was prepared by solid-state reaction over the range 1 {le} x {le} 1.75. Powder preparations of PbV{sub 6}O{sub 11}, however, were always accompanied by a small amount of impurity. The noncentrosymmetric space group P6{sub 3}mc of PbV{sub 6}O{sub 11}, which has an R-block structure, remains unchanged with iron substitution. The crystal structure, remains unchanged with iron substitution. The crystal structure of PbFe{sub 1.75}V{sub 4.25}O{sub 11} was refined from single-crystal X-ray data to R = 0.049. The iron atoms are located preferentially in specific crystallographic sites. The triangular-bipyramidal site is completely occupied by Fe{sup 3+} while the interstices of the central octahedral layer are solely occupied by the vanadium V(1) atoms. The other two crystallographic sites have mixed Fe/V occupancies. Magnetic measurements performed on nearly single-phase PbV{sub 6}O{sub 11} and the iron substituted phases reveal a spin-glass-type behavior with freezing temperatures T{sub f} of 50 and 65 K, respectively. T{sub f} is independent of the iron ratio. This spin-disordered system is attributed to strong frustration occurring in the a-b plane because of the existence of V(1) trimers providing alternatively long and short V-V distances along the a axis. Resistance and Seebeck coefficient measurements indicate p-type conduction above T{sub f} while the system becomes an insulator below T{sub f}. Fe{sup 3+} ions do not participate in the hopping process, and they block conduction parallel to the c axis because of their location in the bridging dimeric octahedral and bipyramidal sites.
- OSTI ID:
- 577475
- Journal Information:
- Journal of Solid State Chemistry, Vol. 130, Issue 2; Other Information: PBD: May 1997
- Country of Publication:
- United States
- Language:
- English
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