January 24, 2019

Complex Magnets

Measured spin-resolved Fermi surface of fcc cobalt. Spin-resolved photoemission intensities in selected sections through the three-dimensional Fermi surface of 18 ML Co/Cu(100) measured at photon energies of hv = 85 eV (a), hv = 70 eV (b), and hv = 50 eV (c). (d) The fcc Brillouin zone together with the corresponding cuts sampled by (a)–(c). According to the 2D colour code at the lower right, red and blue intensities correspond to majority and minority electronic states 1.

The fundamental understanding of ferromagnetism is crucial to the emergent field of spintronics. Our group tackles the challenge by probing the band structures of ferromagnetic materials which have been the most direct method to explain properties in materials. Recently, our group studied the hitherto unknown non-local electron correlation in an itinerant ferromagnet. Contrary to the assumption of most theoretical models, we demonstrated that non-local electron correlations needed to be taken into account in the manifestation of complex self energy in electronic structure of ferromagnets 1.  

Our group also investigated the generation of spin-polarized electrons from a ferromagnetic 2D electron gas in an ultra-thin ferromagnetic. In this study we employed two-photon photoemission to excite the highly spin-polarized electrons from an ultra-thin cobalt film to majority-spin quantum well states derived from an s p band at the border of the Brillouin zone. 2

(a), (b) Spin-up and spin-down partial intensities obtained in two-photon photoemission from six monolayers of cobalt on Cu(001), remanently magnetized in the M− direction at an intermediate state energy EF + 3.0eV. (c), (d) exchange and spin-orbit contribution to the spin polarization 2 .


  1. Nonlocal electron correlations in an itinerant ferromagnet Tusche, C.; Ellguth, M.; Feyer, V.; Krasyuk, A.; Wiemann, C.; Henk, J.; Schneider, C. M. & Kirschner, J. Nature Communications , Vol. 9 , 2018
  2. Optical Generation of Hot Spin-Polarized Electrons from a Ferromagnetic Two-Dimensional Electron Gas Ellguth, M.; Tusche, C. & Kirschner, J. Physical Review Letters , Vol. 115 , 2015