Neutron Diffraction Study of Metallic Erbium

Neutron diffraction measurements were made on erbium single crystals in the temperature range 298°–4.2°K. The material is antiferromagnetic below 80°K and ferromagnetic below 20°K. In the antiferromagnetic region, the magnetic scattering consists of satellite reflections corresponding to a modulation of the magnetic scattering amplitude along the $c$ axis. The spacing and intensity distribution of these satellites show two distinct subregions of antiferromagnetism. In the upper region, between 80° and 52°K, the data suggest a sinusoidal modulation of the magnitude of the $c$ -axis component of magnetic moment with a period of ${\text{3.5\hspace{0.17em}c}}_0$ . Between 52° and 20°K the wavelength of the modulation varies continuously from ${\text{3.5°\hspace{0.17em}c}}_0$ to ${\text{4.0\hspace{0.17em}c}}_0$ . In addition, there is a squaring up of the modulation and a simultaneous ordering of the component of the moment normal to the $c$ axis. Below 20°K the material is basically ferromagnetic with a moment of 7.2 μB directed parallel to the $c$ axis.