Electrical properties of ferromagnetic Ag:CrO₂ particles

Abstract

A stable silver modified CrO₂, i.e., Ag:CrO₂ of nanocomposite particles was synthesized with a novel chemical method involving Cr⁶⁺, Ag⁺ and NO₃⁻ species in an aqueous solution. A single phase Ag:CrO₂ of submicron size particles (~33 nm average crystallite size) of a Pnnm orthorhombic structure (lattice parameters a = 0.4405 nm, b = 0.4452 nm and c = 0.2885 nm) is obtained after annealing at 573 K in air. Microstructure reveals single domain Ag:CrO₂ particles of prismatic shapes (aspect ratio L/b ~ 1-2) of average b ~30 nm width and 40 to 50 nm length (L). The temperature dependence electrical resistance R (T) shows a phase transition from a metallic to a semiconductor like at a specific temperature TC , which is found to be 405 K at a frequency f = 1 kHz. At 10 kHz, the dielectric constant Ɛr has as large a value as 49, with power loss 0.42. As a function of increasing the f-value, both εr and power loss have been shown to decrease monotonically to the values 28 and 0.06 respectively. The εr gets saturated at f ≥ 400 kHz.