Magnetic Phase Transitions and Lattice Changes in Rare Earth Metals Studied by X-ray Diffraction under a Magnetic Field

The lattice change of the rare earth metals Dy, Ho and Er has been studied by x-ray diffraction under a magnetic field in the c-plane of a hexagonal crystal. Continuous and discontinuous changes of the c-lattice parameter accompanying magnetic phase transitions have been observed in these metals, and satellite reflections caused by the lattice modulation have been found in the distorted helix and helifan phases of Ho and the distorted helix phase of Dy. In Er, the 2nd- and 4th-order satellites appeared below 4.5 T at 35 K, and the 6th-order satellite has been observed above 4.5 T in addition to the 2nd- and 4th-order satellites. These results can be explained with the magnetoelastic effect and the magnetic structure calculated by the self-consistent mean field method, except for the result for Er above 4.5 T at 35 K, where a strongly distorted fan magnetic structure should be assumed to explain the presence of the 6th-order satellite of the lattice modulation.