Oxide electronics

Abstract:

Giant tunability of ferroelectric polarization (ΔP=5000  μC/m2) in the multiferroic GdMn2O5 with external magnetic fields is discovered. The detailed magnetic model from x-ray magnetic scattering results indicates that the Gd-Mn symmetric exchange striction plays a major role in the tunable ferroelectricity of GdMn2O5, which is in distinction from other compounds of the same family. Thus, the highly isotropic nature of Gd spins plays a key role in the giant magnetoelectric coupling in GdMn2O5. This finding provides a new handle in achieving enhanced magnetoelectric functionality.

Abstract:

Magnetic domains at the surface of a ferroelectric monodomain BiFeO3 single crystal have been imaged by hard X-ray magnetic scattering. Magnetic domains up to several hundred microns in size have been observed, corresponding to cycloidal modulations of the magnetization along the wave-vector k=2\pi(\delta,\delta,0) and symmetry equivalent directions. The rotation direction of the magnetization in all magnetic domains, determined by diffraction of circularly polarized light, was found to be unique and in agreement with predictions of a combined approach based on a spin-model complemented by relativistic density-functional simulations. Imaging of the surface shows that the largest adjacent domains display a 120 degree vortex structure.

Abstract:

Spin-lattice coupling and ferroelectric polarization associated with the magnetic ordering in a geometrically frustrated delafossite AgFeO2 have been studied by high resolution neutron powder diffraction and dielectric measurements. The cycloidal magnetic ground state found in this material and the character of the lattice distortions are unprecedented in the family of the delafossite compounds, implying a peculiar mechanism lifting the geometrical frustration. © 2013 Owned by the authors, published by EDP Sciences.