Multiferroicity in V-doped PbTiO3

We report ab initio predictions on the proper multiferroic (ferromagnetic, insulating and ferroelectric) character of PbTiO3 doped with vanadium (V). Ferromagnetically coupled V impurities carry a magnetization of 1 mu B each. The coupling is expected to be strong, since the paramagnetic solution is higher by 150 meV/vanadium, and no stable antiferromagnetic solution was found. The electronic gap in the doped system is about 0.2-0.3 eV in the generalized gradient approximation (GGA), hence the system is properly multiferroic. V doping increases the spontaneous polarization in PbTiO3, with an approximate percentual rate of 0.7 mu C/cm(2).