In-situ studies of large magnetostriction in DyCo₂ compound by synchrotron-based high-energy X-ray diffraction

Synchrotron-based high-energy X-ray diffraction is used to explore the physical origin of large magnetostriction in DyCo₂, an RT₂ compound (R = rare earth, T = Co, Fe), by tracing the crystal structural change as a function of temperature and magnetic field. When the DyCo₂ compound is zero-field cooled down below the Curie temperature T_C, the high-temperature cubic lattice is distorted into a tetragonal structure, associated with an expansion of unit cell volume. When a magnetic field is applied gradually from 0 to 6 T below T_C, no changes in the peak positions for tetragonal (800)_T and (008)_T peaks are observed, whereas their relative peak intensities are gradually changed. The intensity changes generated during magnetic field increasing are reversed stepwise with decreasing the magnetic field. Our experimental results suggest that the large magnetostriction in DyCo₂ is caused by the crystallographic domain-switch mechanism (or rearrangement of tetragonal domains). The diffraction elastic strain is not detected under the field up to 6 T. The present investigations provide a fundamental understanding of the mechanisms of the large magnetostriction in RT₂ compounds with Laves phases.