We have studied the effect of Ca-doping in single-crystal Tb1−xCaxMnO3(x≤0.1) on the crystal and magnetic structure, magnetocapacitance, and electric polarization. For low doping (x=0.05), the presence of Mn4+ ions gives rise to a state with behavior resembling that of a relaxor ferroelectric. The coherence length of the Mn magnetic spin spiral is reduced, while the Mn-modulation wave vector is unchanged. For doping larger than 5%, the ferroelectric state is suppressed, which we ascribe to breakdown of the spiral magnetic structure.
|Number of pages
|Physical Review B (Condensed Matter and Materials Physics)
|Published - 11 Jul 2008