Antiferromagnetism and Electrical Resistivity of Chromium Alloys Containing Ruthenium and Osmium

Abstract

Electrical resistivity ρ has been studied as a function of temperature T of chromium alloys containing 0.9, 2.1, 3.0, and 4.8 at.% Ru and 0.3, 0.6, 1.1, and 2.0 at.% Os. The onset of antiferromagnetism causes large anomalies in the ρ vs T curve. The Néel temperatures T_N of both alloy systems increase rapidly with increasing solute concentrations up to 2 at.%, remain approximately constant, and then decrease with larger solute contents. The initial increase in T_N with increasing solute concentration can be understood by Fedders and Martin's theory assuming that additions of Ru and Os to Cr cause an increase in the electron jack and a decrease in the hole octahedron which enlarge the interaction area of the two Fermi surfaces. The incommensurable antiferromagnetic structure in both alloy systems exists up to about 0.5 at.%. For higher concentrations the antiferromagnetic phase, bordering the paramagnetic region, is commensurable with the lattice. The large increases in the electrical resistivity of the commensurable antiferromagnetic alloys is interpreted as resulting from the superlattice boundaries. For incommensurable phase alloys the resistivity anomaly is due to mutual annihilation of hole and electron Fermi structures.