Energies and Lifetimes of Magnons in Complex Ferromagnets: A First-Principle Study of Heusler Alloys

Abstract

The energies and lifetimes of magnons in several Mn-based Heusler alloys are studied using linear response density functional theory. The number of the spin wave branches in Co(2)MnSi corresponds to the number of its magnetic sublattices in contrast with the NiMnSb case in which the induced Ni sublattice cannot support optical magnons. The half-metallicity of these systems results in long-living acoustic spin waves. The example of non-half-metallic Cu(2)MnAl shows that the hybridization with Stoner continuum leads not only to the damping of magnons but also to a renormalization of their energies.

Superconducting pairing mediated by spin fluctuations from first principles

“…III C, we propose a local approximation for the particlehole propagator. In this limit the equation for the self-energy becomes very transparent: SFs enter via the magnetic response functions, which can be calculated effectively [67,72] within linear response TD-DFT, and the coupling to the electrons is mediated by the exchange-correlation kernel.…”

Ab initio calculations and synthesis of the off-stoichiometric half-Heusler phase Ni1−xMn1+xSb

“…State of the art ab initio studies have shown the magnetization dynamics to be dominated by the Mn moment, with Ni only aligning itself to the fields of Mn atoms. 24 If Ni atoms could be replaced by other atoms with more robust magnetic moments and stronger magnetic interactions, the thermal dependence of magnetic properties of the material is likely to be altered.…”

Long-living terahertz magnons in ultrathin metallic ferromagnets

“…If there are no low-energy Stoner excitations, with energies in the range of magnons' energy, the Landau damping will be inoperative and magnons shall live for a longer time. In principle, in ferro(i)magnetic insulators, for example, yttrium iron garnet 19 , or half metals, for example, Heusler alloys 8,9,15 , the low-energy Stoner excitations are not allowed (in insulators, the density of states of both spin-up and spin-down electrons near the Fermi level is zero; and in half metals, the density of states of one spin character near the Fermi level is zero). Therefore, one expects that the Landau damping is not operative and hence terahertz magnons shall exhibit a long lifetime.…”

“…This means that the use of high-frequency (terahertz) magnons would provide a great opportunity for the design of ultrafast devices. However, one of the main challenges for using terahertz magnons is their short lifetime in metallic ferromagnets [5][6][7][8][9][10][11][12][13][14][15][16] . Hence, the discovery of a low-damping material would push the progress in the field of terahertz magnonics one big step further.…”