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 c rystal. Continuous and discontinuous changes of the c-lattice parameter acc ompanying magnetic phase transitions have been observed in these metals, an d 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 die 6th-order satellite has been observed above 4.5 T in addition t o the 2nd- and 4th-order satellites. These results can be explained with th e magnetoelastic effect and the magnetic structure calculated by the self-c onsistent 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 dth-order satellite of the lattice modulation.