12 research outputs found
Effects of spatially engineered Dzyaloshinskii-Moriya interaction in ferromagnetic films
The Dzyaloshinskii-Moriya interaction (DMI) is a chiral interaction that
favors formation of domain walls. Recent experiments and ab initio calculations
show that there are multiple ways to modify the strength of the interfacially
induced DMI in thin ferromagnetic films with perpendicular magnetic anisotropy.
In this paper we reveal theoretically the effects of spatially varied DMI on
the magnetic state in thin films. In such heterochiral 2D structures we report
several emergent phenomena, ranging from the equilibrium spin canting at the
interface between regions with different DMI, over particularly strong
confinement of domain walls and skyrmions within high-DMI tracks, to advanced
applications such as domain tailoring nearly at will, design of magnonic
waveguides, and much improved skyrmion racetrack memory
Paths to collapse for isolated skyrmions in few-monolayer ferromagnetic films
Magnetic skyrmions are topological spin configurations in materials with
chiral Dzyaloshinskii-Moriya interaction (DMI), that are potentially useful for
storing or processing information. To date, DMI has been found in few bulk
materials, but can also be induced in atomically thin magnetic films in contact
with surfaces with large spin-orbit interactions. Recent experiments have
reported that isolated magnetic skyrmions can be stabilized even near room
temperature in few-atom thick magnetic layers sandwiched between materials that
provide asymmetric spin-orbit coupling. Here we present the minimum-energy path
analysis of three distinct mechanisms for the skyrmion collapse, based on ab
initio input and the performed atomic-spin simulations. We focus on the
stability of a skyrmion in three atomic layers of Co, either epitaxial on the
Pt(111) surface, or within a hybrid multilayer where DMI nontrivially varies
per monolayer due to competition between different symmetry-breaking from two
sides of the Co film. In laterally finite systems, their constrained geometry
causes poor thermal stability of the skyrmion toward collapse at the boundary,
which we show to be resolved by designing the high-DMI structure within an
extended film with lower or no DMI
Thermodynamically self-consistent non-stochastic micromagnetic model for the ferromagnetic state
In this work, a self-consistent thermodynamic approach to micromagnetism is
presented. The magnetic degrees of freedom are modeled using the
Landau-Lifshitz-Baryakhtar theory, that separates the different contributions
to the magnetic damping, and thereby allows them to be coupled to the electron
and phonon systems in a self-consistent way. We show that this model can
quantitatively reproduce ultrafast magnetization dynamics in Nickel.Comment: 5 pages, 3 figure
Fast micromagnetic simulations on GPU : recent advances made with mumax³
In the last twenty years, numerical modeling has become an indispensable part of magnetism research. It has become a standard tool for both the exploration of new systems and for the interpretation of experimental data. In the last five years, the capabilities of micromagnetic modeling have dramatically increased due to the deployment of graphical processing units (GPU), which have sped up calculations to a factor of 200. This has enabled many studies which were previously unfeasible. In this topical review, we give an overview of this modeling approach and show how it has contributed to the forefront of current magnetism research
Phenomenological description of the nonlocal magnetization relaxation in magnonics, spintronics, and domain-wall dynamics
A phenomenological equation called Landau-Lifshitz-Baryakhtar (LLBar)
equation, which could be viewed as the combination of Landau-Lifshitz (LL)
equation and an extra "exchange damping" term, was derived by Baryakhtar using
Onsager's relations. We interpret the origin of this "exchange damping" as
nonlocal damping by linking it to the spin current pumping. The LLBar equation
is investigated numerically and analytically for the spin wave decay and domain
wall motion. Our results show that the lifetime and propagation length of
short-wavelength magnons in the presence of nonlocal damping could be much
smaller than those given by LL equation. Furthermore, we find that both the
domain wall mobility and the Walker breakdown field are strongly influenced by
the nonlocal damping.Comment: 10 pages, 6 figure