Scanning Microwave Microscopy Subsurface Detection of Magneto-Impedance Effect in Thin Film Permalloy

Permalloy-based thin films are ferromagnetic materials with excellent magnetic properties, and their detection is appealing for several applications. Here, a Scanning Microwave Microscope is used to characterize a 15 nm film permalloy (Py) layer buried below 5 nm Aluminum (Al). An ad-hoc experimental setup for reduced parasitics and high-sensitivity operation proved to be an excellent platform to probe the sample magnetic response with nanometer spatial resolution. In particular, magneto-impedance effects, i.e. the high-frequency electrical impedance change due to an externally applied magnetic field, have been captured at 11.1 GHz by microwave spectroscopy, and subsequently studied for various magnetic field intensities. The achieved combination of microwave tomography, high-resolution imaging, and magnetic response detection is challenging for other characterization tools; this provides the foundation to characterize modern multilayered and nanostructured magnetic devices with this tool.