ELECTRICAL-RESISTIVITY STUDIES OF CR-IR ALLOY SINGLE-CRYSTALS

Electrical resistivity has been measured for four Cr-Ir alloy single c rystals for concentrations between 0.07 and 0.25 at.% Ir in the temper ature range 4 to 1200 K. Well defined magnetic anomalies were observed at the Neel temperature (T-N) of each alloy as well as at the incomme nsurate-commensurate (I-C) spin-density-wave (SDW) phase transition te mperature of a Cr + 0.20 at.% Ir ahoy. The latter transition is hyster etic, of hysteresis width about 20 K, which is indicative of a first-o rder ISDW-CSDW phase transition. Analyses of the data show that the fr action of the electron and hole Fermi surface sheets that nests is rou ghly the same in the ISDW and CSDW phases. A magnetic contribution to the resistivity, amounting to between 20% and 25% of the total resisti vity at the Neel point, is observed in the alloys. This contribution, probably due to spin-fluctuation effects, persists to temperatures wel l above T-N, up to about 2.5T(N).