Dielectric signature of charge order in lanthanum nickelates

Three charge-ordering lanthanum nickelates La 2− x A x NiO 4 , substituted with specific amounts of A = Sr, Ca, and Ba to achieve commensurate charge order, are investigated using broadband dielectric spectroscopy up to GHz frequencies. The transition temperatures of the samples are characterized by...

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Veröffentlicht in:The European physical journal. B, Condensed matter physics Condensed matter physics, 2012-07, Vol.85 (7), Article 235
Hauptverfasser: Sippel, P., Krohns, S., Thoms, E., Ruff, E., Riegg, S., Kirchhain, H., Schrettle, F., Reller, A., Lunkenheimer, P., Loidl, A.
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Sprache:eng
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Zusammenfassung:Three charge-ordering lanthanum nickelates La 2− x A x NiO 4 , substituted with specific amounts of A = Sr, Ca, and Ba to achieve commensurate charge order, are investigated using broadband dielectric spectroscopy up to GHz frequencies. The transition temperatures of the samples are characterized by additional specific heat and magnetic susceptibility measurements. We find colossal magnitudes of the dielectric constant for all three compounds and strong relaxation features, which partly are of Maxwell-Wagner type arising from electrode polarization. Quite unexpectedly, the temperature-dependent colossal dielectric constants of these materials exhibit distinct anomalies at the charge-order transitions. This phenomenon is ascribed to a variation of intrinsic material properties affecting the formation of depletion layers at the electrode-sample interfaces.
ISSN:1434-6028
1434-6036
DOI:10.1140/epjb/e2012-30183-2