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Title: Magnetism in nanoparticle LaCoO3

Neutron scattering and magnetometry measurements have been used to study phase transitions in LaCoO3 (LCO). For H <= 100 Oe, evidence for a ferromagnetic (FM) transition is observed at T-c approximate to 87 K. For 1 kOe <= H <= 60 kOe, no transition is apparent. For all H, Curie-Weiss analysis shows predominantly antiferromagnetic (AFM) interactions for T > T-c, but the lack of long-range AFM order indicates magnetic frustration. We argue that the weak ferromagnetism in bulk LCO is induced by lattice strain, as is the case with thin films and nanoparticles. The lattice strain is present at the bulk surfaces and at the interfaces between the LCO and a trace cobalt oxide phase. The ferromagnetic ordering in the LCO bulk is strongly affected by the Co-O-Co angle (gamma), in agreement with recent band calculations which predict that ferromagnetic long-range order can only take place above a critical value, gamma C. Consistent with recent thin film estimations, we find gamma C = 162.8 degrees. For gamma > gamma C, we observe power-law behavior in the structural parameters. gamma decreases with T until the critical temperature, T-o approximate to 37 K; below T-o the rate of change becomes very small.more » For T < T-o, FM order appears to be confined to regions close to the surfaces, likely due to the lattice strain keeping the local Co-O-Co angle above gamma C.« less
Authors:
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Publication Date:
OSTI Identifier:
1163963
Report Number(s):
LBNL-6685E
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: JOURNAL OF PHYSICS-CONDENSED MATTER; Journal Volume: 25; Related Information: Journal Publication Date: 2013
Research Org:
Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY SPIN-STATE; NANOPARTICLES; LA1-XSRXCOO3; LA1-XSR(X)COO3; TEMPERATURE