Shape of magnetic domain walls formed by coupling to mobile charges

Abstract

Magnetic domain walls, which are crucially important in both fundamental physics and technical applications, often have a preference in their form due to many different origins, such as the crystalline shape, lattice symmetry, and magnetic anisotropy. We theoretically investigate yet another origin stemming from the coupling to mobile charges in itinerant magnets. Performing a large-scale numerical simulation in a minimal model for itinerant magnets, i.e., the Kondo lattice model with classical localized spins, we show that the shape of magnetic domain walls depends on the electronic band structure and electron filling. While Néel and 120• antiferromagnetic states do not show a strong preference in the shape of domain walls, noncoplanar spin states with scalar chiral ordering have distinct directional preferences of the domain walls depending on the electron filling. We find that the directional preference is rationalized by the wave-number dependence of the effective magnetic interactions induced by the mobile charges, which are set by the band structure and electron filling. We also observe that, in the noncoplanar chiral states, an electric current is induced along the domain walls owing to the spin Berry phase mechanism, with very different spatial distributions depending on whether the bulk state is metallic or insulating.

Gradient-based stochastic estimation of the density matrix

“…in analogy to Eq. (17). The constraint c(m) = c(n) is only satisfied for orbitals m and n whose real-space distance satisfies r mn S 1/d , and thus introduces a nontrivial dependence on S.…”

Multiple- Q magnetic orders in Rashba-Dresselhaus metals

“…This recently-developed method, called KPM-LD, costs only O(N ) (N : number of lattice sites), allowing us to run the simulation for the system sizes of up to ∼ 10 4 sites. Here we employ the modified version of the KPM-LD [20] making use of a probing method [30] and the stochastic Landau-Lifshitz-Gilbert equation in the LD.…”

Dynamical Switching of Magnetic Topology in Microwave-Driven Itinerant Magnet

“…Here F (ε − µ) is the free energy of the system, and ρ(ε, {S i }) is the density of state of conduction electrons for a given set of the local magnetizations {S i }. To calculate Ω and its magnetization-derivatives ∂Ω/∂S i , we adopt the kernel polynomial method, which is based on the Chebyshev polynomial expansion of Ω and the automatic differentiation [89][90][91][92][93][94][95].…”