Interpretation of electrical conductance transition of hematite in the spin-flip magnetic transition temperature range

Patermarakis, G; Papaioannou, J; Karayianni, H; Masavetas, K

dc.contributor.author	Patermarakis, G	en
dc.contributor.author	Papaioannou, J	en
dc.contributor.author	Karayianni, H	en
dc.contributor.author	Masavetas, K	en
dc.date.accessioned	2014-03-01T01:20:39Z
dc.date.available	2014-03-01T01:20:39Z
dc.date.issued	2004	en
dc.identifier.issn	0013-4651	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/16005
dc.subject	Electric Conductivity	en
dc.subject.classification	Electrochemistry	en
dc.subject.classification	Materials Science, Coatings & Films	en
dc.subject.other	Dipoles	en
dc.subject.other	Photoanodes	en
dc.subject.other	Spin reorientation	en
dc.subject.other	Spin-flip processes	en
dc.subject.other	Anisotropy	en
dc.subject.other	Magnetic susceptibility	en
dc.subject.other	Magnetization	en
dc.subject.other	Photocatalysis	en
dc.subject.other	Polycrystalline materials	en
dc.subject.other	Spectroscopy	en
dc.subject.other	Strain	en
dc.subject.other	Electric conductivity	en
dc.title	Interpretation of electrical conductance transition of hematite in the spin-flip magnetic transition temperature range	en
heal.type	journalArticle	en
heal.identifier.primary	10.1149/1.1768549	en
heal.identifier.secondary	http://dx.doi.org/10.1149/1.1768549	en
heal.language	English	en
heal.publicationDate	2004	en
heal.abstract	Using polycrystalline pure hematite at frequencies of 100 Hz-100 kHz and temperatures of 190-350 K impedance spectroscopy was employed to investigate the electrical conductance transition and correlate it with magnetic transition occurring within this temperature range. A background of slight impurity donor or acceptor semiconductivity was observed above which a peak of conductivity appeared in the temperature range of magnetic transition. The results suggested that the transition from antiferro-magnetically to weak ferromagnetically coupled Fe3+ and vice versa takes place through their transformation to uncoupled Fe3+ and an equilibrium between these types of coupled and uncoupled pairs of Fe3+ is established. A model, thermodynamically sustained, involving bulk concentration of both types of coupled and of uncoupled Fe3+ was formulated precisely predicting the dependence of magnetic transition on temperature and the appearance of peaks in both the uncoupled Fe3+ concentration and conductivity within the transition temperature range. The conductivity, mainly due to intrinsic semiconductance coming from the activation of uncoupled Fe3+, depends on both temperature and concentration of uncoupled Fe3+. The heretofore elusive semiconductive character of hematite is explained. © 2004 The Electrochemical Society. All rights reserved.	en
heal.publisher	ELECTROCHEMICAL SOC INC	en
heal.journalName	Journal of the Electrochemical Society	en
dc.identifier.doi	10.1149/1.1768549	en
dc.identifier.isi	ISI:000222969500070	en
dc.identifier.volume	151	en
dc.identifier.issue	8	en
dc.identifier.spage	J62	en
dc.identifier.epage	J68	en