{sup 139}La NMR in lanthanum manganites: Indication of the presence of magnetic polarons from spectra and nuclear relaxations

Journal Article · Thu Jan 01 04:00:00 EST 1998 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.57.1024· OSTI ID:565909

Allodi, G; De Renzi, R; Guidi, G ^[1]

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1. Dipartimento di Fisica e Istituto Nazionale di Fisica della Materia, Universita di Parma, 43100 Parma (Italy)

We present {sup 139}La NMR experiments on five powder samples of lanthanum manganites, with a Mn{sup 4+} concentration ranging from the antiferromagnetic-insulator (AFM) to the ferromagnetic-conducting (FM) region of the phase diagram. We measure a positive hyperfine coupling C=0.13 T/{mu}{sub B}. A signal from nuclei in a FM environment is present at all compositions, as evidenced by a hyperfine frequency in zero-field experiments, by a positive hyperfine shift in NMR experiments below T{sub c}, and by a paramagnetic frequency shift following Curie-Weiss law. A signal from nuclei in an AFM environment is identified by a similar negative intercept Curie-Weiss law. The NMR spectra reveal a large temperature dependent fraction of static spin defects below T{sub c} in the FM domains. Nuclear relaxation indicates that the FM regions are influenced by diffusing, AFM-correlated excitations, while the AFM regions probe spin fluctuations from diffusing, FM correlated excitations. These results are interpreted in terms of electronic inhomogeneities due to the presence of a magnetic small polaron. {copyright} {ital 1998} {ital The American Physical Society}

• OSTI ID: 565909
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 2 Vol. 57; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ANTIFERROMAGNETIC MATERIALS
COUPLING
EXCITATION
FLUCTUATIONS
HYPERFINE STRUCTURE
LANTHANUM 139
LANTHANUM COMPOUNDS
MANGANESE OXIDES
NMR SPECTRA
POLARONS
SPIN-LATTICE RELAXATION