Structure of Gd, Dy, and Er at Low Temperatures

The crystal structures of gadolinium, dysprosium, and erbium metals have been determined over a wide temperature range. The metals are hexagonal close packed and the $a_0$ unit axis contracts nearly linearly with decreasing temperature, whereas the $c_0$ unit axis exhibits an abnormal expansion with decreasing temperature below magnetic transformations of the metals. The $c_0$ behavior is believed to be associated with the magnetic properties of the metals.