Antiferromagnetism and electrical resistivity of dilute chromium-germanium alloys

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Abstract
Electrical resistivity from 4 to 700 K is reported for dilute Cr alloys containing 0.35, 1.1, 1.4, and 2.2 at.% Ge. The implications of this study for the magnetic phase diagram of Cr-Ge alloys are compared with recent results from thermal expansion measurements by Suzuki, and agree with the existence of a magnetic triple point at ∼0.35 at.% Ge. Contrary to the rigid-band hypothesis, Ge acts as an electron donor when substituted into the Cr matrix. We argue that this puzzling result can be understood in terms of virtual impurity levels lying above the Fermi level of Cr. Identical considerations are shown to hold for Si impurities in Cr, and may account for the anomalous residual resistance and pronounced resistivity enhancements seen at the Néel temperatures of these alloys.