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Charge transfer processes and magnetoresistance in strontium ferromolybdate with dielectric barriers
Author(s) -
Kalanda N. A.,
Kovalev L. V.,
Zheludkevich M. L.,
Garamus V. M.,
Willumeit R.,
Sobolev N. A.
Publication year - 2013
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201200888
Subject(s) - electrical resistivity and conductivity , magnetoresistance , condensed matter physics , annealing (glass) , curie temperature , materials science , thermal conduction , grain boundary , dielectric , conductivity , analytical chemistry (journal) , magnetic field , chemistry , ferromagnetism , metallurgy , physics , microstructure , optoelectronics , quantum mechanics , composite material , chromatography
The Sr 2 FeMoO 6− δ 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 Sr 2 FeMoO 6− δ in applied magnetic fields up to 8 T. The compound was synthesized out of partially reduced SrFeO 3− x , SrMoO 4− y precursors (sample I). At the first oxidation stage upon annealing at 700 K in argon with a partial oxygen pressure p (O 2 ) = 10 Pa for 15 h (sample II), the internal structure of the Sr 2 FeMoO 5.82 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 T mB the conductivity is predominantly metallic, whereas below T mB down to 4.2 K 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 Sr 2 FeMoO 5.82 grains.