Differences between the multiferroic properties of hexagonal and orthorhombic ion-doped YFeO3 nanoparticles

The multiferroic properties of ion-doped hexagonal and orthorhombic YFeO3 (YFO) nanoparticles (NPs) are studied theoretically. The magnetization M-s in h-YFO NPs increases, whereas for o-YFO NPs it decreases with decreasing NP size. In the dielectric constant (DC) both h- and o-YFO have a peak around T-C1 similar to 450 and 460 K, respectively, but only in h-YFO an anomaly appears at T-C2 similar to 300 K in the DC and the polarization which could be connected with a possible P6(3)mc-P63cm phase transition. The polarization in pure and Bi-doped o-YFO NPs increases with increasing magnetic field. M-s(x) is studied by doping of a o-YFO NP with Ti4+ ions at the octahedral Fe3+ sites. M-s(T) in undoped YFO shows a small kink at TC1 similar to 450 K, whereas in the doped YFO it shows at similar to 480 K. By different ion doping on the Y or Fe sites in YFO there is a transformation from the h- to the o-phase or vice versa. In M-n-doped o-YFO a spin-reorientation transition appears. The bandgap of h-YFO is smaller compared to that of o-YFO.