The overall behaviour of these bands is in good agreement with the calculation of ground state electronic structure. Although the PES intensity at Fermi level is very low because of the role played by polarons, a dispersion of the Fe 3d-t2g states is observed.
#PHOTOLINE SLC PLUS#
A band structure calculation using generalized gradient approximation plus U (GGA+U) to the density functional theory (DFT) is proposed to explain the experimental results. This thesis presents spin- and angle-resolved photoemission studies on the magnetic and electronic structure of Fe3O4 (001) epitaxially grown on MgO (001).
But up to now, any clear experimental evidence is lacking. This ferrimagnet with a high Curie temperature has been theoretically predicted to be a half-metal with a conductive minority-spin (↓) channel and a semiconductive majority-spin (↑) channel, resulting in 100 % spin polarization at the Fermi level. Magnetite (Fe3O4) is a promising candidate for application in spintronic devices. In fact, the spin-polarization dynamics in momentum space show that these states display macroscopically different temperatures and, more importantly, different cooling rates over several picoseconds. We propose that the newly reported state plays a major role in the ultrafast dynamics of the system, acting as a bottleneck for the interaction between the topologically protected surface state and the bulk conduction band. Our experiments reveal the existence of a surface resonance state in the second bulk band gap that is benchmarked by fully relativistic ab initio spin-resolved photoemission calculations. In this Letter we show that only measuring the spin intensity signal over several orders of magnitude by spin-, time-, and angle-resolved photoemission spectroscopy can provide a comprehensive description of the optically excited electronic states in Bi 2 Se 3.
The prospect of optically inducing and controlling a spin-polarized current in spintronic devices has generated wide interest in the out-of-equilibrium electronic and spin structure of topological insulators. Through the present work, we aim to prove that Heusler compounds provide an excellent playground to study fundamental magnetism and offer a pathway for future materials design. Finally, structural and magnetic properties of Mn3Ga/Co2YZ Heusler superlattices are investigated in order to combine ultralow Gilbert damping coefficient, minority spin band gap and perpendicularly magnetized heterostructures, another requirement for low energy consumption devices. This way, it is possible to confront theoretical models unifying those two quantities that live in different timescales. Then, the relation between the Gilbert damping and the ultrafast demagnetization time in quaternary Co2MnSixAl1-x compounds with a tunable spin polarization is analyzed. The ultralow magnetic damping coefficients measured in the range from 4.1 x10-4 to 9 x10-4 for Co2MnSi, Co2MnGe, Co2MnSn and Co2MnSb are the lowest values ever reported in conductive layers and offer a clear experimental demonstration of theoretical predictions on half metal magnetic Heusler compounds. Experimental results allow us to directly explore the interplay of spin polarization, spin gap and Fermi energy position, with the magnetic damping obtained in these films (together with predictions from ab initio calculations).
By substitution of the Z element in high quality Co2MnZ (Z=Al, Si, Ga, Ge, Sn and Sb) epitaxial thin films grown by molecular beam epitaxy, electronic properties such as the minority-spin band gap, Fermi energy position in the band gap, and spin polarization can be tuned and the consequences for magnetization dynamics analyzed. The prediction of ultralow magnetic damping in Co2MnZ Heusler half-metal magnets is explored in this study and the damping response is shown to be linked to the underlying electronic structure. In particular, magnetization reversal by spin-orbit and spin-transfer torque as well as the development of spin waves based devices have placed the Gilbert magnetic damping coefficient as a key parameter for future data storage and information processing technologies. Improvements in thin film elaboration methods and a deeper understanding of condensed matter physics have led to new exciting phenomena in spin electronics (spintronics). Due to the low efficiency of common spin detectors of about \(10^\) %. Spin- and \(k\)-resolved hard X-ray photoelectron spectroscopy (HAXPES) is a powerful tool to probe bulk electronic properties of complex metal oxides.
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