Physics – Condensed Matter – Materials Science
Scientific paper
2009-01-05
Journal of Alloys and Compounds, 479 (2009) 11-16
Physics
Condensed Matter
Materials Science
21 pages (including 9 separate figures), submitted to J. of Alloys and Compounds
Scientific paper
10.1016/j.jallcom.2008.12.082
Submicron powder of CrO$_2$ was prepared by hydrothermal synthesis method from chromium trioxide. Particles obtained were of rounded form with mean diameter about 120 nm. The powder (stabilized with thin surface layer of \beta-CrOOH) has been characterized by structural, X-ray and magnetic measurements. The powder (with Curie temperature about 385 K) was cold-pressed and its transport and magnetotransport properties have been measured in the temperature range 4--450 K in magnetic field up to 1.6 T. The samples studied is characterized by non-metallic temperature behavior of resistance and large negative magnetoresistance (MR) in low temperature range. At T=5 K the MR magnitude has been -17% at H=0.3 T and -20% at H=1.4 T. Its magnitude decreased fast with increase in temperature reducing to 0.3% and less for T>200 K. It is shown that this MR behavior is inherent for a system of magnetic grains with spin-dependent intergrain tunnelling. Some peculiarities of MR behavior in low-temperature range (below 40 K) can be associated with percolating character of tunnelling conductivity of this granular system under conditions of availability of only few conducting current paths through the sample.
Belevtsev B. I.
Beliayev Yu. E.
Dalakova N. V.
Osmolowsky M. G.
Selutin A. A.
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