Field dependent magnetization of BiFeO3 in ultrathin La0.7Sr0.3MnO3/BiFeO3 superlattice

We report the observation of field-induced magnetization of BiFeO3 (BFO) in an ultrathin BFO/La0.7Sr0.3MnO3 (LSMO) superlattice using polarized neutron reflectivity (PNR). Our PNR results indicate parallel alignment of magnetization across BFO/LSMO interfaces. The study showed an increase in average magnetization on increasing applied magnetic field at 10K. We observed a saturation magnetization of 110 \pm 15 kA/m (~0.8 {\mu}B/Fe) for ultrathin BFO layer (~2 unit cell) sandwiched between ultrathin LSMO layers (~ 2 unit cell), which is much higher than the canted moment (0.03 {\mu}B/Fe) in the bulk BFO. The macroscopic VSM results on superlattice clearly indicate superparamagnetic behavior typically observed in nanoparticles of manganites.