Spin polarons in La{sub 1-x}Sr{sub x}CoO{sub 3} single crystals.
Nanoscale inhomogeneity in La{sub 1-x}Sr{sub x}CoO{sub 3} has been investigated in single-crystal samples for 0.05 {le} x {le} 0.30 using {sup 139}La and {sup 59}Co NMR to probe local magnetization. In contrast to polycrystalline samples, single crystals exhibit ferromagnetism only above the metal-insulator critical concentration x{sub C} = 0.17. However, over the entire doping range, the single crystals exhibit an unusually broad and asymmetric distribution of hyperfine fields, evidencing (local) spin-polaron formation that persists to temperatures as high as 200 K, well above the glass transition reported previously from bulk magnetization. Above x{sub C} the asymmetry decreases rapidly with increasing doping as polarons overlap to give rise to long-range ferromagnetism. A modified phase diagram is presented. The key features of the data are reproduced by a simple model in which Sr dopants trigger spin-polaron formation, a physical picture first proposed by de Gennes [Phys. Rev. 118, 141 (1960)].
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); National Science Foundation (NSF); State of Florida
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 947531
- Report Number(s):
- ANL/MSD/JA-60875; TRN: US0901442
- Journal Information:
- Phys. Rev. B, Vol. 78, Issue 2008; ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- ENGLISH
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