AbstractThe clear understanding of exchange interactions between magnetic ions in substituted BiFeO₃ is the prerequisite for the comprehensive studies on magnetic properties. BiFe_0.5Mn_0.5O₃ films and BiFeO₃/BiMnO₃ superlattices have been fabricated by pulsed laser deposition on (001) SrTiO₃ substrates. Using piezoresponse force microscopy (PFM), the ferroelectricity at room temperature has been inferred from the observation of PFM hysteresis loops and electrical writing of ferroelectric domains for both samples. Spin glass behavior has been observed in both samples by temperature dependent magnetization curves and decay of thermo-remnant magnetization with time. The magnetic ordering has been studied by X-ray magnetic circular dichroism measurements and Fe-O-Mn interaction has been confirmed to be antiferromagnetic (AF). The observed spin glass in BiFe_0.5Mn_0.5O₃ films has been attributed to cluster spin glass due to Mn-rich ferromagnetic (FM) clusters in AF matrix, while spin glass in BiFeO₃/BiMnO₃ superlattices is due to competition between AF Fe-O-Fe, AF Fe-O-Mn and FM Mn-O-Mn interactions in the well ordered square lattice with two Fe ions in BiFeO₃ layer and two Mn ions in BiMnO₃ layer at interfaces.