Probing Multiferroic Heterostructures of BiFeO₃-LiMn₂O₄ Using Magnetic, Piezoelectric and Piezomagnetic Force Microscopies

In this study magnetic force microscopy (MFM), piezoresponse force microscopy (PFM), and the newly developed piezomagnetic force microscopy (PmFM) techniques are used to probe the ferroelectric and ferromagnetic properties of BiFeO₃-LiMn₂O₄ (BFO-LMO) heterostructures at nano-scale. The PmFM technique is also used to probe the ferromagnetic properties of CoFe₂O₄ (CFO) as a case study. The PFM and PmFM mappings of the BFO-LMO heterostructures clearly distinguish the BFO matrix and LMO nanopillars while the MFM mapping is ambiguous. The relatively high piezomagnetic response of BFO matrix is believed to be due to the Mn doping while the piezoelectric-like response of LMO nanopillars is due to the ionic activities and the vertical geometry of its heterostructure. Lastly, limitations of the PmFM technique are discussed.