Effect of the external fields on the polar and dielectric properties of Eu0.8Y0.2MnO3

Eu0.8Y0.2MnO3 has been widely studied due to its very distinctive phase diagram, where it is still poorly understood the actual ferroelectric character of the low temperature magnetic phases. In order to figure out what is the origin of the microscopic mechanisms that drive its behavior, we carried out a detailed study of the displacement currents for both different starting conditions and polarizing electric fields, and of the field dependent magnetodielectric effect in Eu0.8Y0.2MnO3 ceramics. The experimental results provide clear evidence for the existence of two dipolar systems, one stemming from an electric field-induced process, likely associated with the isovalent substitution of Eu3+ by the smaller off-center Y3+ ions at A-lattice sites, which is independent of any cooperative phenomena occurring in the system. The other dipolar system, strongly dependent on the existence of the first one, drives the polar behavior of the nonmodulated magnetic phase AFM-2, stable in the temperature range of 23-30 K, and is associated with the ferroelectric character of this phase. The magnetic field dependence of the complex dielectric constant clearly shows that the magnetodielectric effect is strongly dependent on the phase it is being considered, and provides further evidence for the ferroelectric character of the AFM-2 phase referred to above.