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

•Orientation of β′-(Sm,Gd)2(MoO4)3 crystals patterned by laser was examined using TEM observations.•The origin of periodic birefringence changes was clarified.•Gradual rotation of crystallographic axes of crystals occurs.•A unique crystal growth with a spiral-like rotation is realized.•The laser-induced crystallization provides a new crystal growth engineering.

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.

Graphical abstractThis figure shows a schematic model for the relationship between the crystallographic axes of β′-(Sm,Gd)2(MoO4)3 crystals and the periodic bright and dark color regions in the line patterned by laser irradiations. Gradual rotation of crystallographic axes of crystals takes place along the crystal growth direction. The origin of periodic birefringence changes is clarified in this study.Figure optionsDownload full-size imageDownload as PowerPoint slide