Magnetic interactions in BiFe(0.5)Mn(0.5)O(3) films and BiFeO(3)/BiMnO(3) superlattices

The clear understanding of exchange interactions between magnetic ions in substituted BiFeO(3) is the prerequisite for the comprehensive studies on magnetic properties. BiFe(0.5)Mn(0.5)O(3) films and BiFeO(3)/BiMnO(3) superlattices have been fabricated by pulsed laser deposition on (001) SrTiO(3) 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(0.5)Mn(0.5)O(3) films has been attributed to cluster spin glass due to Mn-rich ferromagnetic (FM) clusters in AF matrix, while spin glass in BiFeO(3)/BiMnO(3) 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 BiFeO(3) layer and two Mn ions in BiMnO(3) layer at interfaces.