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 applications. 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, allowing 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 magnetization. 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 conditions 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 existing detection systems, enabling spin-, angle-, and energy-resolved photoemission experiments as add-on functionality.