Development of hard x-ray photoelectron SPLEED-based spectrometer applicable for probing of buried magnetic layer valence states

TL;DR

This paper introduces a high-voltage compatible spin-resolved hard x-ray photoelectron spectrometer capable of probing buried magnetic layers, demonstrated through valence state analysis of a FeCo tunneling device with detailed spin polarization spectra.

Contribution

A novel high-voltage compatible polarimeter design for spin-resolved HAXPES, enabling analysis of buried magnetic layers' valence states with high transmission and simultaneous spin detection.

Findings

First spin-resolved data for buried FeCo layer

Validation of Spin-HAXPES for bulk electronic structure

Rich spin polarization spectra with discernible transitions

Abstract

A novel design of high-voltage compatible polarimeter for spin-resolved hard x-ray photoelectron spectroscopy (Spin-HAXPES) went into operation at beamline BL09XU of SPring-8 in Hyogo, Japan. The detector is based on the well-established principle of electron diffraction from a W(001) single-crystal at a scattering energy of 103.5 eV. Its special feature is that it can be operated at a high negative bias potential up to 10 kV, necessary to access the HAXPES range. The polarimeter is operated behind a large hemispherical analyzer (Scienta R-4000). It was optimized for high transmission of the transfer optics. The exit plane of the analyzer contains a delay-line detector (20 mm dia.) for conventional multichannel intensity spectroscopy simultaneously with single-channel spin analysis. The performance of the combined setup is demonstrated by the first spin-resolved data for the valence-region of a FeCo functional layer of a tunneling device, buried beneath 3 nm of oxidic material. The well-structured spin polarization spectrum validates Spin-HAXPES in the valence energy range as powerful method for bulk electronic structure analysis. The spin polarization spectrum exhibits a rich structure, originating from clearly discernible transitions in the majority and minority partial spin spectra.