ﻻ يوجد ملخص باللغة العربية
We performed magnetic and ferroelectric measurements, first principle calculations and Landau theory analysis on hexagonal YMnO3. The polarization and the AFM order parameter were found to present different temperature dependence at TN. A linear coupling between these two order parameters is thus forbidden in the Landau theory and P63cm cannot be the magnetic group. The only compatible magnetic group is P63. In this group however, Landau theory predicts the possibility of a ferromagnetic component and of a linear coupling between the dielectric constant and the AFM order parameter. On one hand we performed dielectric constant measurements under magnetic field that clearly exhibit a metamagnetic transition, and thus confirm these predictions. On the other hand careful magnetization measurements show a small by non null FM component along the c-axis direction. Finally the Landau analysis within the P63 magnetic group shows that only the polarization square is coupled to the magnetic orders and thus neither the magnetization nor the AFM order can be reversed by an applied electric field.
We performed magnetic and ferroelectric measurements, associated with Landau theory and symmetry analysis, in order to clarify the situation of the YMnO3 system, a classical example of type I multiferroics. We found that the only magnetic group compa
The commensurate $p/q$-filled $n$-component Hubbard chain was investigated by bosonization and high-precision density-matrix renormalization-group analysis. It was found that depending on the relation between the number of components $n$, and the fil
We used Raman and terahertz spectroscopies to investigate lattice and magnetic excitations and their cross-coupling in the hexagonal YMnO3 multiferroic. Two phonon modes are strongly affected by the magnetic order. Magnon excitations have been identi
Inspired by the experimental findings of an exotic ferromagnetic insulating state in LaMnO$_3$/SrTiO$_3$ heterostructures, we calculate the electronic and magnetic state of LaMnO$_3$/SrTiO$_3$ superlattices with comparable thicknesses employing ab-in
The magnetic structures which endow TbMnO$_3$ with its multiferroic properties have been reassessed on the basis of a comprehensive soft x-ray resonant scattering (XRS) study. The selectivity of XRS facilitated separation of the various contributions