arXiv subjects

Anna Delin

Publications and source records attributed to Anna Delin.

78 records · Page 5Linked to original sources

arXiv2013

Thermally excited spin waves in a nano-structure: thermal gradient vs. constant temperature

Using micromagnetic simulations, we have investigated spin dynamics in a nanostructure in the presence of thermal fluctuations. In particular, we have studied the effects of a uniform temperature and of a uniform thermal gradient. In both cases, the stochastic field leads to an increase of the precession angle of the magnetization, and to a mild decreas of the linewidth of the resonance peaks. Our results indicate that the Gilbert damping parameter plays the role of control parameter for the amplification of spin waves.

cond-mat.mes-hall↗

arXiv2012

Density functional theory study of the electronic structure of fluorite Cu$_{2}$Se

We have investigated the electronic structure of fluorite Cu$_{2}$Se using density functional theory calculations within the LDA, PBE and AM05 approximations as well as with the non-local hybrid PBE0 and HSE approximations. Our results show that Cu$_{2}$Se is a zero gap semiconductor when using either a local or semi-local density functional approximation while there exists a gap when using the PBE0 functional. For the HSE approximation, we find that the presence of a gap depends on the range separation for the non-local exchange within the HSE approximation. For the occupied states we find that the LDA, PBE, AM05, PBE0 and HSE agrees when regarding the overall structure, however, the hybrid functionals are shifted towards lower energy values compared to the LDA, PBE and AM05. The valence bands obtained using the hybrid functionals are in good agreement with experimental valence band spectra. We also find that the PBE, PBE0 and HSE approximations give similar results regarding bulk properties, such as lattice constants and bulk modulus. In addition, we have investigated the localization of the Cu d-states and its effect on the band gap in the material using the LDA+U approach. We find that a gap is opened up by increasing the $U$, however, the $U$ values required for a gap opening is unrealistically high.

cond-mat.mtrl-sci↗

arXiv2005

Effect of electron correlations in Pd, Ni, and Co monowires

We investigated the effect of mean-field electron correlations on the band electronic structure of Co, Ni, and Pd ultra-thin monatomic nanowires, at the breaking point, by means of density-functional calculations in the self-interaction corrected LDA approach (LDA+SIC) and alternatively by the LDA+$U$ scheme. We find that adding static electron correlations increases the magnetic moment in Pd monowires, but has negligible effect on the magnetic moment in Co and Ni. Furthermore, the number of $d$-dominated conductance channels decreases somewhat compared to the LDA value, but the number of $s$-dominated channels is unaffected, and remains equal to one per spin.

cond-mat.mtrl-sci↗

arXiv2004

Emerging nanomagnetism in 4d transition metal nanowires

Monatomic nanowires of the nonmagnetic transition metals Ru, Rh, and Pd have been studied theoretically, using first-principles computational techniques, in order to investigate the possible onset of magnetism in these nanosystems. Our fully relativistic spin-polarized all-electron density functional calculations reveal the onset of Hund's rule magnetism in nanowires of all three metals, with mean-field moments of 1.1, 0.3, and 0.7 bohr magnetons, respectively, at the equilibrium bond length. An analysis of the band structures indicates that the nanocontact superparamagnetic state suggested by our calculations should affect the ballistic conductance between tips made of Ru, Rh or Pd, leading to possible temperature and magnetic field dependent conductance.

cond-mat.mtrl-sci↗

arXiv2004

Emerging Magnetism in Platinum Nanowires

We have investigated infinitely long, monostrand Pt nanowires theoretically, and found that they exhibit Hund's rule magnetism. We find a spin moment of 0.6 Bohr magnetons per atom, at the equilibrium bond length. Its magnetic moment increases with stretching. The origin of the wire magnetism is analyzed and its effect on the conductance through the wire is discussed.

cond-mat.mtrl-sci↗

arXiv2003

Magnetic phenomena in 5d transition metal nanowires

We have carried out fully relativistic full-potential, spin-polarized, all-electron density-functional calculations for straight, monatomic nanowires of the 5d transition and noble metals Os, Ir, Pt and Au. We find that, of these metal nanowires, Os and Pt have mean-field magnetic moments for values of the bond length at equilibrium. In the case of Au and Ir, the wires need to be slightly stretched in order to spin polarize. An analysis of the band structures of the wires indicate that the superparamagnetic state that our calculations suggest will affect the conductance through the wires -- though not by a large amount -- at least in the absence of magnetic domain walls. It should thus lead to a characteristic temperature- and field dependent conductance, and may also cause a significant spin polarization of the transmitted current.

cond-mat.mtrl-sci↗