Magnetoelectric effect and low-temperature phase transitions in YMn2O5

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Abstract
A possibility of ferroelectricity has been proposed in some low temperature phases of the oxides of the series RMn2O5 (R = a rare earth from Nd to Lu, Y or Bi). YMn2O5 is unusual in this series, because Y3+ is non-magnetic. We made dielectric, magnetic and magnetoelectric measurements on single crystals of this oxide to detect two electric transitions at 39 K and 19 K. These transitions are accompanied with anomalies in the dielectric constant and the magnetic and the magnetoelectric susceptibilities. Particularly, the sign of the magnetoelectric susceptibility is switched below 19 K, depending on the sense of the electric field applied during cooling the sample down to 4.2 K. This fact indicates that YMn2O5 possesses spontaneous polarization at least below 19 K.