NPs using First Order Reversal Curves*

BiFeO₃ (BFO) in bulk is ferroelectric (FE) and antiferromagnetic (AF) at room temperature. Additional it also possesses a Dzyaloshinski-Moria (DM) anisotropy that produces a 62 nm wavelength spin spiral. Therefore, in nanostructured BFO systems, a complex ferromagnetism-like behavior appears that depends on the balance between size and magnetic length scales . Furthermore, it is known that the physical properties in perovskites in general, and BFO in particular, are very sensitive to changes in their crystal structure. Hence, one can exploit such effects to control their degrees of freedom. Here we present first-order reversal curves (FORC) as a reliable method to deconvolute the BFO magnetic contributions that appear when nanostructured in the form of nanoparticles with sizes below and above the wavelength spin spiral . We use FORC to obtain coercivity distributions for different nanoparticles sizes. Our results suggest two main contributions to BFO magnetism that can be related to an intrinsic core-shell structure that forms due to strain relaxation.