Magnetic properties of single-crystal uranium mononitride

Abstract

The susceptibility of a single crystal of antiferromagnetic uranium mononitride (TN ≃ 53 K) is reported between 4 and 1000 K. The paramagnetic susceptibility follows a modified Curie-Weiss law with a temperature-independent susceptibility χ0=8.0×10−6 emu cm−3 added, ϑ=−247 K, and 2.66 Bohr magnetons/U atom. Nearest and next nearest neighbor exchange constants are evaluated. The anisotropy in the ordered region is discussed on the basis of an equal distribution of antiferromagnetic domains with spin direction along any of the three 〈100〉 axes. Such an assumption is corroborated by thermal expansion measurements along the three 〈100〉 axes.