Antiferromagnetism and Electrical Transport Properties of Chromium-Aluminum Alloys

Electrical resistivity ρ of Cr–Al alloys containing 0.3-, 1.2-, 1.9-, 3.7-, and 6.2-at.% Al has been studied as a function temperature. The onset of antiferromagnetism causes small anomalies in the ρ vs T curves from which the Néel temperature TN can be determined. TN decreases rapidly with additions of small amounts of Al and then increases with larger Al concentrations. A minimum in the TN vs Al content curve occurs at about 1.2-at.% Al. This minimum results from the fact that below about 1.5-at.% Al level, the Cr–Al alloys possess an incommensurable antiferromagnetic structure. Above this concentration, the antiferromagnetic phase is of the commensurable type. The absolute thermoelectric power measurements on alloys containing 0.3 and 1.2-at.% Al support the determinations of TN from the electrical resistivity studies.