Ferroelectricity in perovskite $HoMn{O}_3$ and $YMn{O}_3$

B. Lorenz, Y. Q. Wang, C. W. Chu

Ferroelectricity is observed in orthorhombic $HoMn{O}_3$ and $YMn{O}_3$ at the magnetic lock-in transitions into an E-type structure or an incommensurate phase with a temperature indep…