Differential Magnetic Force Microscopy with a Switchable Tip

We report the design and demonstration of a magnetic force microscopy probe whose tip magnetization can be switched by a short current pulse applied to a coil. The tip is characterized in a magnetic force microscope using a Co/Pt thin-film sample on a flat cantilever. We perform in situ differential MFM imaging with single switching pulses down to 40 us. We also demonstrate continuous switching of the tip magnetization in the range of a few Hz to a few kHz, and detection of the magnetic information at the corresponding sideband. We are currently working on incorporating the switchable tip in a membrane-based force microscope with the long-term goal of performing ultrasensitive nuclear spin detection.