18 research outputs found
Spin relaxation signature of colossal magnetic anisotropy in platinum atomic chains
Recent experimental data demonstrate emerging magnetic order in platinum
atomically thin nanowires. Furthermore, an unusual form of magnetic anisotropy
-- colossal magnetic anisotropy (CMA) -- was earlier predicted to exist in
atomically thin platinum nanowires. Using spin dynamics simulations based on
first-principles calculations, we here explore the spin dynamics of atomically
thin platinum wires to reveal the spin relaxation signature of colossal
magnetic anisotropy, comparing it with other types of anisotropy such as
uniaxial magnetic anisotropy (UMA). We find that the CMA alters the spin
relaxation process distinctly and, most importantly, causes a large speed-up of
the magnetic relaxation compared to uniaxial magnetic anisotropy. The magnetic
behavior of the nanowire exhibiting CMA should be possible to identify
experimentally at the nanosecond time scale for temperatures below 5 K. This
time-scale is accessible in e.g., soft x-ray free electron laser experiments.Comment: 9 pages, 3 figure
A theoretical analysis of inertia-like switching in magnets: applications to a synthetic antiferromagnet
The magnetization dynamics of a synthetic antiferromagnet subject to a short
magnetic field pulse, has been studied by using a combination of
first-principles and atomistic spin dynamics simulations. We observe switching
phenomena on the time scale of tens of picoseconds, and inertia-like behavior
in the magnetization dynamics. We explain the latter in terms of a dynamic
redistribution of magnetic energy from the applied field pulse to other
possible energy terms, such as the exchange interaction and the magnetic
anisotropy, without invoking concepts such as inertia of an antiferromagnetic
vector. We also demonstrate that such dynamics can also be observed in a
ferromagnetic material where the incident field pulse pumps energy to the
magnetic anisotropy
Spin-lattice couplings in a skyrmion multilayers of Pd-Fe/Ir(111)
Pd-Fe/Ir(111) has attracted tremendous attention for next-generation
spintronics devices due to existence of magnetic skyrmions with the external
magnetic field. Our density functional theoretical calculations in combination
with spin dynamics simulation suggest that the spin spiral phase in fcc stacked
Pd-Fe/Ir(111) flips into the skyrmion lattice phase around B 6 T.
This leads to the microscopic understanding of the thermodynamic and kinetic
behaviours affected by the intrinsic spin-lattice couplings (SLCs) in this
skyrmion material for magneto-mechanical properties. Here we calculate fully
relativistic SLC parameters from first principle computations and investigate
the effect of SLC on dynamical magnetic interactions in skyrmion multilayers
Pd-Fe/Ir(111). The exchange interactions arising from next nearest-neighbors
(NN) in this material are highly frustrated and responsible for enhancing
skyrmion stability. We report the larger spin-lattice effect on both dynamical
Heisenberg exchanges and Dzyaloshinskii-Moriya interactions for next NN
compared to NN which is in contrast with recently observed spin-lattice effect
in bulk bcc Fe and CrI monolayer. Based on our analysis, we find that the
effective measures of SLCs in fcc (hcp) stacking of Pd-Fe/Ir(111) are and times stronger for NN and next
NN respectively, compared to bcc Fe. The linear regime of displacement for SLC
parameters is 0.02 {\AA} which is 0.72\% of the lattice constant for
Pd-FeIr(111). The microscopic understanding of SLCs provided by our current
study could help in designing spintronic devices based on thermodynamic
properties of skyrmion multilayers.Comment: 8(main text)+4(appendix) pages and 5(main text)+4(appendix) figure
Magnon softening in a ferromagnetic monolayer: a first-principles spin dynamics study
We study the Fe/W(110) monolayer system through a combination of first
principles calculations and atomistic spin dynamics simulations. We focus on
the dispersion of the spin waves parallel to the [001] direction. Our results
compare favorably with the experimental data of Prokop et al. [Phys. Rev. Lett.
102, 177206], and correctly capture a drastic softening of the magnon spectrum,
with respect to bulk bcc Fe. The suggested shortcoming of the itinerant
electron model, in particular that given by density functional theory, is
refuted. We also demonstrate that finite temperature effects are significant,
and that atomistic spin dynamics simulations represent a powerful tool with
which to include these.Comment: v1: 11 pages, 3 figures. v2: double column, 5 pages, 3 figures, typos
corrected, references adde
General method for atomistic spin-lattice dynamics with first-principles accuracy
We present a computationally efficient and general first-principles based method for spin-lattice simulations for solids and clusters. The method is based on a coupling of atomistic spin dynamics and molecular dynamics simulations, expressed through a spin-lattice Hamiltonian, where the bilinear magnetic term is expanded up to second order in displacement. The effect of first-order spin-lattice coupling on the magnon and phonon dispersion in bcc Fe is reported as an example, and we observe good agreement with previous simulations. We also illustrate the coupled spin-lattice dynamics method on a more conceptual level, by exploring dissipation-free spin and lattice motion of small magnetic clusters (a dimer, trimer, and tetramer). The method discussed here opens the door for a quantitative description and understanding of the microscopic origin of many fundamental phenomena of contemporary interest, such as ultrafast demagnetization, magnetocalorics, and spincaloritronics
Magnetism in AV3Sb5 (Cs, Rb, K): Origin and Consequences for the Strongly Correlated Phases
The V-based kagome systems AV3Sb5 (A = Cs, Rb and K) are unique by virtue of
the intricate interplay of non-trivial electronic structure, topology and
intriguing fermiology, rendering them to be a playground of many mutually
dependent exotic phases like charge-order and superconductivity. Despite
numerous recent studies, the interconnection of magnetism and other complex
collective phenomena in these systems has yet not arrived at any conclusion.
Using first-principles tools, we demonstrate that their electronic structures,
complex fermiologies and phonon dispersions are strongly influenced by the
interplay of dynamic electron correlations, non-trivial spin-polarization and
spin-orbit coupling. An investigation of the first-principles-derived
inter-site magnetic exchanges with the complementary analysis of q-dependence
of the electronic response functions and the electron-phonon coupling indicate
that the system conforms as a frustrated spin-cluster, where the occurrence of
the charge-order phase is intimately related to the mechanism of
electron-phonon coupling, rather than the Fermi-surface nesting.Comment: Accepted in Physical Review Letter
Magnetism in AV3Sb5 (A = Cs, Rb, K): Complex Landscape of the Dynamical Magnetic Textures
We have investigated the dynamical magnetic properties of the V-based kagome
stibnite compounds by combining the ab-initio calculated magnetic parameters of
a spin Hamiltonian like inter-site exchange parameters, magnetocrystalline
anisotropy and site projected magnetic moments, with full-fledged simulations
of atomistic spin-dynamics. Our calculations reveal that in addition to a
ferromagnetic order along the [001] direction, the system hosts a complex
landscape of magnetic configurations comprised of commensurate and
incommensurate spin-spirals along the [010] direction. The presence of such
chiral magnetic textures may be the key to solve the mystery about the origin
of the experimentally observed inherent breaking of the C6 rotational symmetry-
and the time-reversal symmetry.Comment: Accepted In Physical Review