FastMag: Fast micromagnetic simulator for complex magnetic structures (invited)

Abstract

A fast micromagnetic simulator (FastMag) for general problems is presented. FastMag solves the Landau-Lifshitz-Gilbert equation and can handle problems of a small or very large size with a high speed. The simulator derives its high performance from efficient methods for evaluating the effective field and from implementations on massively parallel Graphics Processing Unit (GPU) architectures. FastMag discretizes the computational domain into tetrahedral elements and therefore is highly flexible for general problems. The magnetostatic field is computed via the superposition principle for both volume and surface parts of the computational domain. This is accomplished by implementing efficient quadrature rules and analytical integration for overlapping elements in which the integral kernel is singular. Thus discretized superposition integrals are computed using a non-uniform grid interpolation method, which evaluates the field from N sources at N collocated observers in () ON operations. This approach allows handling any uniform or non-uniform shapes, allows easily calculating the field outside the magnetized domains, does not require solving linear system of equations, and requires little memory. FastMag is implemented on GPUs with GPU-CPU speed-ups of two orders of magnitude. Simulations are shown of a large array and a recording head fully discretized down to the exchange length, with over a hundred million tetrahedral elements on an inexpensive desktop computer.

Quantitative simulation of temperature-dependent magnetization dynamics and equilibrium properties of elemental ferromagnets

“…Design requirements for magnetic devices typically require complex combinations of sample geometry, tuned material properties and dynamic behavior to optimize their performance. Understanding the complex interaction of these physical effects often requires numerical simulations such as those provided by micromagnetics [12][13][14] or atomistic spin models 15 . Micromagnetic simulations at elevated temperatures 16,17 in addition need the temperature dependence of the main parameters 18 such as the magnetization, micromagnetic exchange 19 and effective anisotropy 20 .…”

Micromagnetics on high-performance workstation and mobile computational platforms

“…4 FastMag is a Finite Element Method (FEM) based micromagnetic simulator that is intended for solving problems of high geometrical and material complexity. FastMag's flexibility and performance rely on several advanced computational methods, including fast evaluation of effective fields, fast evaluation of the system Jacobian, efficient time integration, efficient methods for system discretization, and the ability to run on various computing platforms.…”

“…In particular, GPUs were introduced offering ultra-high performance, which allowed using inexpensive desktop computers as highperformance computer clusters. [4][5][6][7][8] Recently, new embedded mobile-based computer architectures emerged, and their performance increase has been higher than that of desktop CPU and GPU systems. In addition, embedded systems offer low power consumption and manufacturing cost.…”

“…An important component in enabling the analysis and design of complex magnetic devices is the development of parallel computational codes. [1][2][3][4][5][6][7][8] Multiple parallel platforms have been used in Micromagnetics, including multi-core central processing units (CPU) and graphics processing units (GPUs). In particular, GPUs were introduced offering ultra-high performance, which allowed using inexpensive desktop computers as highperformance computer clusters.…”

Integrated Broadband Bowtie Antenna on Transparent Silica Substrate

“…In addition, the resonant frequency of a bowtie antenna can be designed and tuned by appropriately modifying and scaling the bowtie geometry, such as its arm length, flare angle, and feed gap width. This enables the bowtie antenna to have various applications over a wide frequency range, including extremeultraviolet light generation [2], optical antennas [3,16,5], Terahertz-wave optoelectronics [17], mid-infrared plasmonic antennas and sensors [8,18], microwave radar [7], wireless communications [4,19], flexible RF devices [20], complex electromagnetic structures [21], and photonic detection of freespace electromagnetic waves [22][23][24].…”