Investigation of the Magnetic Structure of ErMn2, TmMn2, TbNi2 by Neutron Diffraction

Abstract

Magnetic measurements by H. J. Williams (ErMn₂ and TmMn₂), and W. E. Wallace (TbNi₂) have shown that these compounds are magnetically ordered at low temperature with a net moment per formula unit lower than that of the free rare‐earth ion. Neutron diffraction powder patterns have been used to determine the actual magnetic structure. ErMn₂ and TmMn₂ crystallize with the hexagonal Laves phase structure (C‐14 type). ErMn₂ is ferromagnetic, with a moment of 7.72 μ_B/Er atom at 4.2°K aligned along the c axis. No detectable moment on Mn is observed. TmMn₂ is almost completely ferromagnetic, with a moment of 4.95 μ_B/TM atom at 2.1°K aligned along the c axis, and essentially zero moment for Mn. A faint additional line at low angle seems to indicate a weak antiferromagnetic contribution. TbNi₂ crystallizes with the cubic Laves phase structure (C‐15 type). At 4.2°K, ferromagnetic lines as well as additional peaks appear in the diffraction pattern, but the magnetic scattering is rather sensitive to sample preparation.