Magnetoresistance in Cobalt Whiskers

Abstract

Measurements of magnetoresistance in cobalt whiskers with residual resistance ratios up to 400 have been made in the temperature range 1°–4.2°K and in magnetic fields up to 80 kOe. Field dependence curves give evidence of magnetic breakdown above 65 kOe for certain field and current orientations. Shubnikov-deHaas oscillations in the longitudinal magnetoresistance indicate the existence of small pockets of the Fermi surface that contribute directly to the oscillatory magnetoresistance with periods of 9.3×10−7 G−1, 2.8×10−7 G−1, and 8.6×10−8 G−1, respectively. The larger period of 9.3×10−7 G−1 is in approximate agreement with the period observed by Reed and Fawcett in the transverse oscillatory magnetoresistance above 70 kOe. The temperature dependence of resistivity in the range 1°–4.2°K at H̄=0 is given by ρ∝αT2 with α=15×10−12 Ω cm/deg2. At 50 kOe the coefficient of the T2 coefficient increases by 33%.