skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

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

Abstract

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}

Authors:
; ;  [1]
  1. Dipartimento di Fisica e Istituto Nazionale di Fisica della Materia, Universita di Parma, 43100 Parma (Italy)
Publication Date:
OSTI Identifier:
565909
Resource Type:
Journal Article
Journal Name:
Physical Review, B: Condensed Matter
Additional Journal Information:
Journal Volume: 57; Journal Issue: 2; Other Information: PBD: Jan 1998
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; LANTHANUM COMPOUNDS; MANGANESE OXIDES; POLARONS; NMR SPECTRA; LANTHANUM 139; ANTIFERROMAGNETIC MATERIALS; HYPERFINE STRUCTURE; EXCITATION; FLUCTUATIONS; COUPLING; SPIN-LATTICE RELAXATION

Citation Formats

Allodi, G, De Renzi, R, and Guidi, G. {sup 139}La NMR in lanthanum manganites: Indication of the presence of magnetic polarons from spectra and nuclear relaxations. United States: N. p., 1998. Web. doi:10.1103/PhysRevB.57.1024.
Allodi, G, De Renzi, R, & Guidi, G. {sup 139}La NMR in lanthanum manganites: Indication of the presence of magnetic polarons from spectra and nuclear relaxations. United States. https://doi.org/10.1103/PhysRevB.57.1024
Allodi, G, De Renzi, R, and Guidi, G. 1998. "{sup 139}La NMR in lanthanum manganites: Indication of the presence of magnetic polarons from spectra and nuclear relaxations". United States. https://doi.org/10.1103/PhysRevB.57.1024.
@article{osti_565909,
title = {{sup 139}La NMR in lanthanum manganites: Indication of the presence of magnetic polarons from spectra and nuclear relaxations},
author = {Allodi, G and De Renzi, R and Guidi, G},
abstractNote = {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}},
doi = {10.1103/PhysRevB.57.1024},
url = {https://www.osti.gov/biblio/565909}, journal = {Physical Review, B: Condensed Matter},
number = 2,
volume = 57,
place = {United States},
year = {Thu Jan 01 00:00:00 EST 1998},
month = {Thu Jan 01 00:00:00 EST 1998}
}