Size, external fields and ion doping effects on the multiferroic properties of hexagonal YMnO3 nanoparticles

The size, external field and doping dependence of different properties of hexagonal YMnO3 nanoparticles (NPs) is theoretically investigated. The spontaneous magnetization M-s increases with increasing electric field and decreasing NP size N. The polarization decreases with increasing magnetic field h. The band gap increases with decreasing N. The phonon mode (omega) over bar (0) = 167 cm(-1) shows a kink at T-N due to strong spin-phonon interaction. Applying h the kink disappears. By doping with different ions at the Mn site, due to the observed different strains M-s can increase or decrease. By large Ti ion doping, above a critical x value, is taken into account that there appears a hexagonal-orthorhombic phase transition. The Gd and Sr substitution on the Y place in YMnO3 NPs is also discussed. The dielectric function as a function of temperature, NP size and h is studied. The electron and phonon contributions to the specific heat C-p are shown.

Automated summary

The size, external field, and doping dependence of hexagonal YMnO3 nanoparticles were investigated theoretically. The results showed that the spontaneous magnetization increases with increasing electric field and decreasing nanoparticle size, while the polarization decreases with increasing magnetic field. The band gap also increases with decreasing nanoparticle size, and a strong spin-phonon interaction was observed in the phonon mode. Doping with different ions at the Mn site can either increase or decrease the magnetization depending on the observed strains.