Recently, BiFeO3  multiferroics have drawn a great deal of attention due to their superior ferroelectric properties in epitaxial thin film form in comparison to counterpart bulk single crystals or ceramics. In this work we present the results on magnetic properties of multiferroic ultrathin films (30-300 nm) of BiFeO3, (BiLa)FeO3 and  (BiNd)FeO3  obtained by sputtering in transverse high frequency discharge, vacuum laser oblation and metalorganic chemical vapour deposition  on monocrystalline  substrates of (001) SrTiO3, (100) MgO and  (100) Al2O3. The concentration of Bi, La и Nd in dodecahedral sublattices was varied. A novel effect of treatment of multiferroic films in a negative corona discharge has been investigated. It is demonstrated that the magnetisation may be increased by up to 35%  whilst the change in    is not noticeable. This effect does not depend on neither film composition no technological method. 

Keywords: multiferroics, magneto-electric materials, methods of preparation, the films of bismuth ferrite, pseudomorphic structure, magnetic properties, corona discharge