Unique crystal growth with crystal axis rotation in multi-ferroic β′-(Sm,Gd)2(MoO4)3 narrow lines patterned by lasers in glass Original Research Article

The morphology and orientation of multi-ferroic β′-(Sm,Gd)2(MoO4)3 crystals in the lines patterned by laser irradiations in 3Sm2O3–18.25Gd2O3–63.75MoO3–15B2O3 (mol%) glass were examined using transmission electron microscope (TEM) observations in order to clarify the origin of the appearance of periodic birefringence in an atomic-scale level. The crystallographic direction of crystals in the lines was determined from selected area electron diffraction (SAED) patterns in TEM observations, and it was demonstrated that a gradual rotation of crystallographic axes takes place along the crystal growth direction (laser scanning direction). The unique crystal growth with a spiral-like rotation of the crystallographic axes is due to the gradual rotation of (MoO4)2− tetrahedral units in β′-(Sm,Gd)2(MoO4)3 crystals. The laser-induced crystallization, in which the region and direction of crystal growth are restricted artificially to a narrow space, provides a new crystal growth engineering.