Transport and magnetotransport properties of cold-pressed CrO 2 powder

H. Liu, R. K. Zheng, Y. Wang, H. L. Bai, Xixiang Zhang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

Resistivity of cold-pressed CrO 2 powder has been measured over the temperature range of 2 to 350 K with a magnetic field up of to 50 kOe. High resolution transmission electron microscopy (HRTEM) images show that the CrO 2 particles are needle-shaped with an aspect ratio of 7:1 and have an average length of 200 nm, and are covered with an ultra-thin (∼2.5 nm) native Cr 2 O 3 layer. Temperature dependent conductivity can be well described by the expression exp[-(Δ/T) 1/2 ] below 55 K, a feature of electron tunneling, and by the higher-order hopping for temperature above 55 K. The magnetoresistance, MR = [ρ(max) - ρ(H)]/ρ(max), reaches ∼33.5% at 2 K and decreases to nearly zero at room temperature. Temperature dependent saturation magnetization follows well the relation M(T) = M s (1-BT 3/2 ) below 240 K. The spin-wave stiffness constant, D, is estimated to be ∼91 meV Å 2 . By fitting the specific heat measured in the temperature range of 1.8-34 K by the relation C = γT + βT 3 + β 1 T 5 + αT 3/2 , we obtained the electronic specific heat coefficient γ=1.7 mJ/mol K 2 , this corresponds to a density of states at the Fermi level of 0.73 states/eV, which is in good accordance with the theoretical value of 0.69 states/eV.

Original languageEnglish (US)
Pages (from-to)144-150
Number of pages7
JournalPhysica Status Solidi (A) Applications and Materials Science
Volume202
Issue number1
DOIs
StatePublished - Jan 1 2005

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Electrical and Electronic Engineering
  • Materials Chemistry

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