Transverse Magnetoresistivity ofαandβPlutonium

Transverse magnetoresistivity measurements have been made on pure, polycrystalline $\alpha$ and $\beta$ plutonium. The magnetoresistivity of both phases is negative at 5°K and low applied fields, and becomes positive at fields greater than 2000 G. The negative effect decreases with increasing temperature and is not dependent on sample texture. The higher-field results follow the $H^2$ dependence found in "normal" metals. It is concluded that the negative effect is due to magnetic ordering, which results from $s-f$ exchange, and the Néel temperatures are near 20-30°K for both phases. The high-field data are consistent with earlier models in which the electrical conductivity is dominated by a small number of holes in the $7s$ band.