Magnetic dissipation microscopy in ambient conditions

We have quantified sub-picowatt power losses in very soft (yttrium iron garnets) and relatively hard (metal evaporated tape) ferromagnetic materials associated with dissipative micromagnetic processes during magnetic force microscope imaging. We had a thermally limited power resolution of 2×10−15 W in a 1 kHz bandwidth operating in air. In the epitaxial garnet film, peak dissipation (3×10−13 W) was spatially correlated with domain wall motion induced by the localized field from the tip. In metal-evaporated recording tape imaged with a cantilever coated with 50 nm of CoCr, the dissipation was observed in extremely localized regions of the sample (<10 nm). Absence of dissipation features when using a different tip suggests the dissipation originated in the tip rather than the sample. This technique shows promise for mapping micromagnetic structure and dissipative processes, quantitatively evaluating magnetic force microscope (MFM) tip performance, and for detecting perturbations in MFM images.