Direct Spin-Imaging Detector Based on Freestanding Magnetic Nanomembranes

An analog of the optical polarizer-analyzer for electrons, a spin filter based on a freestanding ferromagnetic (FM) nanomembrane covering the entrance of the microchannel plate (MCP) was applied for efficient spin filtering and electron amplification in the 2D field of view. To study the spin dependent transmission, we constructed a spin-triode device (spintron), which consists of a compact proximity focused vacuum tube with the Na_{2}KSb spin-polarized electron source, the FM-MCP and phosphor screen placed to run parallel to each other. Here, we demonstrate the fabrication of FM nanomembranes consisting of a [Co/Pt] superlattice deposited on a freestanding 3 nm SiO_{2} layer with a total thickness of 10 nm. The FM-MCP has ∼10^{6} channels with a single-channel Sherman function S=0.6 and a transmission of ∼1.5×10^{-3} in the low electron energy range. The FM-MCP-based device provides a compact optical method for measuring the spin polarization of free electron beams in the imaging mode and is well suited for photoemission spectroscopy and microscopy methods.