Magnetic frustration in (LaA)CoNbO{sub 6} (A=Ca, Sr, and Ba) double perovskites
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW (United Kingdom)
The crystal and magnetic structures of the (LaA)CoNbO{sub 6} (A=Ca, Sr, and Ba) double perovskites have been investigated. The A=Ca and Sr compounds crystallize with a monoclinic P2{sub 1}/n superstructure while the larger A=Ba gives a tetragonal I4/m superstructure. These materials have a rocksalt ordered arrangement of Co and Nb with almost no inversion (<1%) for A=Ca and 4% inversion for A=Sr and Ba. Magnetic susceptibility measurements reveal antiferromagnetic ordering transitions with Neel temperatures of 17 K (A=Ca), 16 K (A=Sr), and 10 K (A=Ba). The low temperature antiferromagnetic ordering is described by the magnetic propagation vector k=((1/2) 0 (1/2)) for all materials. The saturated cobalt magnetic moment decreases from 2.97(2) {mu}{sub B} to 2.52(3) {mu}{sub B} to 1.85(5) {mu}{sub B} for A=Ca, Sr, and Ba, respectively. The decrease of ordering temperature and moment with increasing size of A evidences magnetic frustration due to competition between 90 deg. superexchange pathways. This is shown to be a general feature in antiferromagnetic double perovskites.
- OSTI ID:
- 20664946
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 70, Issue 17; Other Information: DOI: 10.1103/PhysRevB.70.174434; (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
ANTIFERROMAGNETIC MATERIALS
ANTIFERROMAGNETISM
BARIUM COMPOUNDS
CALCIUM COMPOUNDS
COBALT COMPOUNDS
LANTHANUM COMPOUNDS
MAGNETIC MOMENTS
MAGNETIC SUSCEPTIBILITY
MONOCLINIC LATTICES
NEEL TEMPERATURE
PEROVSKITES
STRONTIUM COMPOUNDS
TEMPERATURE RANGE 0013-0065 K
TETRAGONAL LATTICES