Antiferromagnetism in Cr3Al and relation to semiconducting behavior

Abstract

Antiferromagnetism and chemical ordering have both been previously suggested as causes of the observed semiconductorlike behavior in Cr3Al. Two films of Cr3Al(001)/MgO(001) were grown under different conditions to achieve different types of chemical ordering and electronic properties: one X-phase structure (semiconducting) and one C11b structure (metallic). The films were investigated by x-ray and neutron diffraction. Both films show commensurate antiferromagnetic order, with a high Néel temperature greater than 578 K, showing that the antiferromagnetism in Cr3Al is quite robust. Density-functional theory calculations were performed and it was shown that the well-known antiferromagnetic pseudogap in the density of states occurs for all types of chemical ordering considered. The conclusion of these studies is that the antiferromagnetism causes a pseudogap in the density of states, which is a necessary condition for the semiconductorlike transport behavior; however, that antiferromagnetism is seen in both metallic and semiconducting Cr3Al samples shows that antiferromagnetism is not a sufficient condition for semiconducting behavior. Chemical ordering is equally important.