Charge transfer processes and magnetoresistance in strontium ferromolybdate with dielectric barriers. Issue 4 (5th April 2013)

• Record Type: Journal Article
• Authors: Kalanda, N. A.; Kovalev, L. V.; Zheludkevich, M. L.; Garamus, V. M.; Willumeit, R.; Sobolev, N. A.
• Is Part Of: Physica status solidi. Volume 250:Issue 4(2013:Apr.)
• Page Start: 825
• Page End: 830
• Publication Date: 2013-04-05
• Subjects: Solid state physics -- Periodicals; Solids -- Periodicals; Atomic structure -- Periodicals; 530.41
• DOI: 10.1002/pssb.201200888
• Languages: English
• ISSNs: 0370-1972

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The Sr<sub>2</sub>FeMoO<sub>6−<italic>δ</italic></sub> 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<sub>2</sub>FeMoO<sub>6−<italic>δ</italic></sub> in applied magnetic fields up to 8 T. The compound was synthesized out of partially reduced SrFeO<sub>3−<italic>x</italic></sub>, SrMoO<sub>4−<italic>y</italic></sub> precursors (sample I). At the first oxidation stage upon annealing at 700 K in argon with a partial oxygen pressure <italic>p</italic>(O<sub>2</sub>) = 10 Pa for 15 h (sample II), the internal structure of the Sr<sub>2</sub>FeMoO<sub>5.82</sub> grains did not change. Sample II exhibits a mixed type of electrical conduction. In a magnetic field <italic>B</italic> its resistivity decreases without changing the mixed regime of charge transport, only shifting the temperature of minimum resistivity (<italic>T</italic><sub>mB</sub>) to lower values. At temperatures above <italic>T</italic><sub>mB</sub> the conductivity is predominantly metallic, whereas below <italic>T</italic><sub>mB</sub> 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 <italic>T</italic> = 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<sub>2</sub>FeMoO<sub>5.82</sub> grains.</p> </abstract>