Charge transfer processes and magnetoresistance in strontium ferromolybdate with dielectric barriers

authors	Kalanda, NA; Kovalev, LV; Zheludkevich, ML; Garamus, VM; Willumeit, R; Sobolev, NA
nationality	International
journal	PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS
author keywords	dielectric interlayer; double perovskite; magnetization; magnetoresistance; microstructure
keywords	MAGNETIC-PROPERTIES; DOUBLE PEROVSKITES; SR2FEMOO6; TRANSITION; DEFECTS
abstract	The Sr2FeMoO6-delta compound attracts the attention of researchers due to a high Curie temperature, large values of negative magnetoresistance at room temperature and a practically 100% spin polarization of conduction electrons. We have studied the role of grain boundaries on the electrical transport in Sr2FeMoO6-delta in applied magnetic fields up to 8 T. The compound was synthesized out of partially reduced SrFeO3-x, SrMoO4-y precursors (sample I). At the first oxidation stage upon annealing at 700K in argon with a partial oxygen pressure p(O-2)-10 Pa for 15 h (sample II), the internal structure of the Sr2FeMoO5.82 grains did not change. Sample II exhibits a mixed type of electrical conduction. In a magnetic field B its resistivity decreases without changing the mixed regime of charge transport, only shifting the temperature of minimum resistivity (T-mB) to lower values. At temperatures above TmB the conductivity is predominantly metallic, whereas below TmB down to 4.2K it is of semiconductor type. The increase of the annealing time up to 30 h (sample III) brings about an increase of the resistivity and the appearance of semiconductor-type conductivity at T 300-4.2 K, which indicates the formation of a continuous insulating interlayer between the grains. In a magnetic field, the resistivity decreases, with the conductivity changing from the semiconducting to a mixed one. In the latter case the charge transport can occur both through point metallic contacts and by means of spin-dependent tunneling across dielectric interlayers between Sr2FeMoO5.82 grains. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
publisher	WILEY-V C H VERLAG GMBH
issn	0370-1972
year published	2013
volume	250
issue	4
beginning page	825
ending page	830
digital object identifier (doi)	10.1002/pssb.201200888
web of science category	Physics, Condensed Matter
subject category	Physics
unique article identifier	WOS:000318791900031