Electron hopping mechanism in hematite (α-Fe2O 3)

Papaioannou, JC; Patermarakis, GS; Karayianni, HS

dc.contributor.author	Papaioannou, JC	en
dc.contributor.author	Patermarakis, GS	en
dc.contributor.author	Karayianni, HS	en
dc.date.accessioned	2014-03-01T01:22:17Z
dc.date.available	2014-03-01T01:22:17Z
dc.date.issued	2005	en
dc.identifier.issn	00223697	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/16512
dc.subject	A. Magnetic materials	en
dc.subject	D. Dielectric properties	en
dc.subject.other	Activation energy	en
dc.subject.other	Antiferromagnetism	en
dc.subject.other	Charge carriers	en
dc.subject.other	Charge transfer	en
dc.subject.other	Dielectric properties of solids	en
dc.subject.other	Electric conductivity of solids	en
dc.subject.other	Iron oxides	en
dc.subject.other	Magnetic materials	en
dc.subject.other	Permittivity	en
dc.subject.other	Phase shift	en
dc.subject.other	Polycrystalline materials	en
dc.subject.other	Relaxation processes	en
dc.subject.other	Single crystals	en
dc.subject.other	Thermal effects	en
dc.subject.other	Electron hopping mechanisms	en
dc.subject.other	Hematite	en
dc.subject.other	Morin temperature	en
dc.subject.other	Reorganization energy	en
dc.subject.other	Electron transitions	en
dc.title	Electron hopping mechanism in hematite (α-Fe2O 3)	en
heal.type	journalArticle	en
heal.identifier.primary	10.1016/j.jpcs.2004.11.002	en
heal.identifier.secondary	http://dx.doi.org/10.1016/j.jpcs.2004.11.002	en
heal.publicationDate	2005	en
heal.abstract	The frequency dependence of the real (ε′) and imaginary (ε″) parts of the dielectric constant of polycrystalline hematite (α-Fe2O3) has been investigated in the frequency range 0-100 kHz and the temperature range 190-350 K, in order to reveal experimentally the electron hopping mechanism that takes place during the Morin transition of spin-flip process. The dielectric behaviour is described well by the Debye-type relaxation (α-dispersion) in the temperature regions T<233 K and T>338 K. In the intermediate temperature range 233 K<T<338 K a charge carrier mechanism takes place (electron jump from the O2- ion into one of the magnetic ions Fe3+) which gives rise to the low frequency conductivity and to the Ω-dispersion. The temperature dependence of relaxation time (τ) in the -ln τ vs 10 3/T plot shows two linear regions. In the first, T<238 K, τ increases with increasing T implying a negative activation energy -0.01 eV, and in the second region T>318 K τ decreases as the temperature increases implying a positive activation energy 0.12 eV. The total reorganization energy (0.12-0.01) 0.11 eV is in agreement with the adiabatic activation energy 0.11 eV given by an ab initio model in the literature. The temperature dependence of the phase shift in the frequencies 1, 5, 10 kHz applied shows clearly an average Morin temperature TMo=284±1 K that is higher than the value of 263 K corresponding to a single crystal due to the size and shape of material grains. © 2004 Elsevier Ltd. All rights reserved.	en
heal.journalName	Journal of Physics and Chemistry of Solids	en
dc.identifier.doi	10.1016/j.jpcs.2004.11.002	en
dc.identifier.volume	66	en
dc.identifier.issue	5	en
dc.identifier.spage	839	en
dc.identifier.epage	844	en