High-field magnetic force microscopy as susceptibility imaging

We describe an extension of variable-temperature magnetic force microscopy (MFM) that allows spatial discrimination between the different states that exist in magnetically phase-separated materials. Some manganites exhibit a micrometer-scale separation of phases that are either ferromagnetic, paramagnetic, or antiferromagnetic. In an applied field large enough to saturate the ferromagnetic phase, any MFM contrast arising from the variation of the magnetization (domain walls, domains of differing orientation) is eliminated, while the nonferromagnetic phases are magnetized according to their susceptibilities. The different phases can then be discerned by their respective contrast levels in the MFM images.