Stress-induced crystal axis spiral rotation in multiferroic β'-Gd 2 (MoO 4) 3 crystals observed only in the crystallization of Gd 2 O 3-MoO 3-B 2 O 3 glasses is a new world of glass-crystallization being beyond the usual crystal growth engineering. The selfpowdering phenomenon in crystals synthesized in an electric furnace and the appearance of periodic birefringence images observed in laser-patterned single crystal lines are reviewed together with some new data. Extremely large stresses are created at the interface between super-cooled liquids and crystals due to the density difference between glasses/liquids with larger density and crystals with smaller density, and the crystal axis spiral rotation is induced in β'-Gd 2 (MoO 4) 3 crystals in order to relax and release stresses at the interface. The structural origin of the density difference between glasses and crystals is discussed, and the uniqueness of the crystallization of Gd 2 O 3-MoO 3-B 2 O 3 glasses is emphasized. The possibility of the synthesis of dense bulk glass-ceramics with β'-Gd 2 (MoO 4) 3 crystals is tried using a slow melt-cooling processing. K E Y W O R D S birefringence imaging, crystal axis spiral rotation, glass crystallization, laser patterning, multiferroic β'-Gd 2 (MoO 4) 3 , self-powdering phenomenon, stress F I G U R E 1 DTA pattern at room temperature for the meltquenched sample with the composition of 21.25Gd 2 O 3-63.75MoO 3-15B 2 O 3 glass (21.25GdMoBO glass). Heating rate was 10 K/min 27 F I G U R E 2 Temperature dependence of magnetic susceptibility (χ M) and inverse susceptibility (χ M −1) for 21.25GdMoBO glass under zero-field cooled (ZFC) and field-cooled (FC) conditions 45 [Color figure can be viewed at wileyonlinelibrary.com] How to cite this article: Komatsu T, Honma T. Stress-induced crystal axis spiral rotation in multiferroic β'-Gd 2 (MoO 4) 3 observed only in glass crystallization.