Resistive, magnetoresistive and magnetic properties of four kinds of pressed powders of CrO2, synthesized from chromic anhydride by the hydrothermal method were investigated. The new synthesis method allows the thickness of dielectric shells to be controlled. The powders consisted of particles (≈ 120 nm in dia.) or acicular crystals (≈ 22.9 nm in dia. and 302 nm in length). All the particles were covered with a surface dielectric shell of different thickness and types (e.g. β-CrOOH oxyhydroxide or chromium oxide Cr2O3). The influence of properties and thickness of intergranular dielectric layers as well as shapes of CrO 2 particles on tunnel resistance and magnetoresistance (MR) of the pressed powders was studied. It was found that at low temperatures all the samples studied displayed a nonmetallic temperature dependence of resistance and a giant negative MR. Maximum values of MR at T ≈ 5 K were ≈ 37% in rather low fields (0.5 T). As temperature was increased, MR decreased rapidly (down to ≈ 1% in field 1 T at T ≈ 200 K). At low temperatures the powders with acicular particles exhibited a new type of MR hysteresis and nonmonotonic dependence of MR with increasing magnetic field (a maximum). A nonmonotonic temperature dependence Hp(T), where Hp being a field in which the resistance is maximal, discrepancies in the values of Hp and coercive force Hc, and anisotropy of MR as a function of mutual orientation of transport current and magnetic field were observed.
|Переведенное название||Resistive and magnetoresistive properties of compacted CrO2 powders with different types of intergranular dielectric layers|
|Журнал||ФИЗИКА НИЗКИХ ТЕМПЕРАТУР|
|Состояние||Опубликовано - 1 дек 2012|
Предметные области Scopus
- Физика и астрономия (все)