Freestanding magnetic membranes on graphene for spin-filtering applications

Spin polarimetry of low-energy electron beams is of considerable importance for a wide range of appli- cations. However, an efficient method for two-dimensional, quantitative spin mapping is still lacking as state-of-art detectors rely on the sequential measurement of the spin polarization at individual points in energy and momentum space. In this work, we exploit the spin-dependent transmission of electrons through ultrathin magnetic layers embedded in a suspended matrix of a few graphene layers, fabricated in the form of micrometric magnetic freestanding membranes with an overall thickness below 10 nm, allow- ing significant transmission of low-energy electrons. We systematically investigate the role of deposition process, number of graphene layers, and magnetic materials with both in-plane and out-of-plane magneti- zation. We end up with optimized fabrication conditions for producing highly reliable elastic membranes with energy-dependent transmittivity suitable for spin filtering. We also present an analytical model that describes the detection of the spin polarization of an electron beam and outlines the experimental con- ditions under which such measurements can be performed using suspended magnetic membranes. This research paves the way for the development of spin filters that can be seamlessly integrated into exist- ing detection systems, enabling spin-, angle-, and energy-resolved photoemission experiments as add-on functionality.