Doping effects of multiferroic manganites YMn0.9 X0.1 O3 (X=Al, Ru, and Zn)

In order to understand the unusual magnetic phase of multiferroic hexagonal manganites, we have investigated the doping effects of hexagonal manganites YMn0.9 X0.1 O3 (X=Al, Ru, and Zn) by using bulk measurements as well as neutron-diffraction experiments. We have also re-examined the magnetic structure of YMnO3 to find that it has mainly the Γ3 representation with an about 18% mixing of the Γ4 representation. Upon doping nonmagnetic atoms such as Al, Ru, and Zn at the Mn site, the mixing of the two representations gets increased with an angle growing between the magnetic moment and the crystallographic a axis (Ø) for example, Ø changes from 10° for YMnO3 to 45° for YMn0.9 Zn0.1 O3. At the same time, the ordered moment becomes significantly reduced with doping, while the transition temperature is suppressed slightly.