Spin Polarimetry

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This research activity aims at developing a two dimensional spin filter to add the spin resolution to k- and energy-resolved photoemission experiments (ARPES), performed at radiation synchrotron facilities. Arrays of free-standing magnetic membranes with nanometric thickness can be effectively employed as spin detectors of electron beams, either generated by an electron gun or photoemitted by a sample [1]. The working principle is the selective transmission of electrons with spin parallel or anti-parallel to a quantization axis defined by the direction of the magnetization of a ferromagnetic layer [2].

A proper fabrication process is employed to obtain the free-standing membranes, that must be (i) thin, (ii) mechanically robust and self-sustaining, (iii) yielding efficient transmission and spin asymmetry, and (iv) with magnetization either in-plane or out-of-plane, to realize a full 3D characterization of the spin direction of the electron beam.

The prototype stage is performed at PoliFab, aiming at optimizing the geometry and the materials of the membranes, by the combined use of deposition, lithography and characterization techniques (including a spin polarized electron gun for the direct measurements of the spin asimmetry [3]). Then, the device will be tested and actively employed on a true photoemission setup, at the APE beamline at the synchrotron light source of Elettra (Trieste) .

References

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  1. Y. Lassailly, H.-J. Drouhin, A. J. van der Sluijs, G. Lampel, and C. Marlière, “Spin-dependent transmission of low-energy electrons through ultrathin magnetic layers”, Phys. Rev. B 50, 13054(R) (1994), doi: 10.1103/PhysRevB.50.13054
  2. T. Övergaard, B.M Wojek, M. Leandersson, H. Ohldag, S. Bonetti, T. Wiell, and O. Tjernberg, “Free-standing magnetic nano-membranes for electron spin-filtering applications”, arXiv:1709.03838
  3. M. Cantoni and R. Bertacco, “High efficiency apparatus for spin polarized inverse photoemission”, Review of Scientific Instruments 75, 2387 (2004) doi: 10.1063/1.1753681

Involved People