Oxide electronics

Abstract:

We have performed dielectric measurements and neutron diffraction experiments on the delafossite AgFeO 2. A ferroelectric polarization P 300μC/m2 was observed in a powder sample, below 9AK. The neutron diffraction experiment demonstrated successive magnetostructural phase transitions at T N1=15K and T N2=9K. The magnetic structure for 9K≤T≤15K is a spin-density wave with a temperature dependent incommensurate modulation k=(-1,q,12), q 0.384. Below 9AK, the magnetic structure turns into elliptical cycloid with the incommensurate propagation vector k=(-12,q,12), q 0.2026 Based on the deduced magnetic point-group symmetry m1 ′ of the low-temperature polar phase, we conclude that the ferroelectric polarization in AgFeO 2 is perpendicular to the monoclinic b axis and is driven by the inverse Dzyaloshinskii-Moriya effect with two orthogonal components p 1 r ij×(S i×S j) and p 2 S i×S j. © 2012 American Physical Society.

Abstract:

Resonant magnetic x-ray scattering has been used to investigate the magnetic structure of the magnetoelectric multiferroic DyMn 2O 5. We have studied the magnetic structure in the ferroelectric phase of this material, which displays the strongest ferroelectric polarization and magnetodielectric effect of the RMn 2O 5 (where R is a rare-earth ion, Y or Bi) family. The magnetic structure observed is similar to that of the other members of the series, but differs in the direction of the ordered moments. In DyMn 2O 5, both the Dy and Mn moments lie close to the b axis, whereas in other RMn 2O 5 they lie close to the a axis. © 2012 American Physical Society.