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- Wessely, Ola, et al.
(författare)
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Current Driven Magnetization Dynamics in Helical Spin Density Waves
- 2006
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 96:25
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Tidskriftsartikel (refereegranskat)abstract
- A mechanism is proposed for manipulating the magnetic state of a helical spin density wave using a current. It is shown that a current through a bulk metal with a helical spin density wave induces a spin transfer torque, which gives rise to a rotation of the order parameter. The use of spin transfer torque to manipulate the magnetization in bulk systems does not suffer from the obstacles seen for magnetization reversal using interface spin transfer torque in multilayered systems. The effect is demonstrated by a quantitative calculation of the current induced magnetization dynamics of a rare earth metal, Er. Finally, we propose a setup for experimental verification.
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- Wessely, Ola, et al.
(författare)
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Dynamical core-hole screening in the x-ray absorption spectra of hydrogenated carbon nanotubes and graphene
- 2007
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 76:16, s. 161402-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We have calculated the electronic structure and the x-ray absorption (XA) spectrum of a hydrogenated single graphite plane, in order to simulate recent experimental results on hydrogenated single wall carbon nanotubes (SWCNT) as well as hydrogenated graphene. We find that the presence of H induces a substantial component of sp3 bonding and as a result the and * components to the electronic structure vanish. We have calculated a theoretical x-ray absorption spectrum using a multiband version of the Mahan-Nozières–De Dominicis theory. By making a fitting of the XA signal of C atoms that have H attached to them and C atoms without H in the vicinity we obtain a good representation of the experimental data and we can draw the conclusion that in the experiments [A. Nikitin et al., Phys. Rev. Lett. 95, 225507 (2005)] some 35–50 % H have been absorbed in the SWCNT.
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- Wessely, Ola, et al.
(författare)
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Initial and final state effects in the x-ray absorption process of La1-xSrxMnO3
- 2003
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Ingår i: Physical Review B : Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 68:23, s. 235109-1
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Tidskriftsartikel (refereegranskat)abstract
- We have probed the electronic structure of La1-xSrxMnO3 using x-ray absorption spectroscopy, and compared our results to theory. It is shown that the O projected spectrum reveals a signal that is consistent only with hybridized and delocalized Mn d-states whereas the Mn projected spectrum reveals a signal that can only be reproduced by atomic like theory allowing for multiplet formation between the core hole and the valence electrons of the final state. Our results indicate that the ground state electronic structure has delocalized Mn d-states. This is discussed to be caused by a dynamical screening of the core hole created in the absorption process.
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- Wessely, Ola, et al.
(författare)
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Spin-Transfer Torque in Helical Spin Density Waves
- 2009
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 79:10, s. 104433-
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Tidskriftsartikel (refereegranskat)abstract
- The current driven magnetization dynamics of a helical spin-density wave is investigated. Expressions for calculating the spin-transfer torque of real systems from first-principles density-functional theory are presented. These expressions are used for calculating the spin-transfer torque for the spin spirals of Er and fcc Fe at two different lattice volumes. It is shown that the calculated torque induces a rigid rotation of the order parameter with respect to the spin spiral axis. The torque is found to depend on the wave vector of the spin spiral and the spin polarization of the Fermi surface states. The resulting dynamics of the spin spiral is also discussed.
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