MALTS: A Tool to Simulate Lorentz Transmission Electron Microscopy From Micromagnetic Simulations

Abstract

Here we describe the development of the MALTS software which is a generalized tool that simulates Lorentz Transmission Electron Microscopy (LTEM) contrast of magnetic nanostructures. Complex magnetic nanostructures typically have multiple stable domain structures. MALTS works in conjunction with the open access micromagnetic software Object Oriented Micromagnetic Framework or MuMax. Magnetically stable trial magnetization states of the object of interest are input into MALTS and simulated LTEM images are output. MALTS computes the magnetic and electric phases accrued by the transmitted electrons via the Aharonov-Bohm expressions.Transfer and envelope functions are used to simulate the progression of the electron wave through the microscope lenses. The final contrast image due to these effects is determined by Fourier Optics. Similar approaches have been used previously for simulations of specific cases of LTEM contrast. The novelty here is the integration with micromagnetic codes via a simple user interface enabling the computation of the contrast from any structure. The output from MALTS is in good agreement with both experimental data and published LTEM simulations. A widely-available generalized code for the analysis of Lorentz contrast is a much needed step towards the use of LTEM as a standardized laboratory technique.

Observation of stable Néel skyrmions in cobalt/palladium multilayers with Lorentz transmission electron microscopy

“…Figure 1e–j shows a simulated tilt series of Néel skyrmion contrast in L-TEM 31 32 . As an input, a micromagnetically simulated Néel skyrmion of radius nominally 100 nm was used.…”

“…This contrast corresponds to the projection of the magnetization that is directed out of the sample plane orthogonal to the beam direction.Fig. 1e-j shows a simulated tilt series of Néel skyrmion contrast in L-TEM31,32 . As an input, a micromagnetically simulated Néel skyrmion of radius nominally 100 nm was used.…”

Single crystalline cylindrical nanowires – toward dense 3D arrays of magnetic vortices

“…LorTEM image simulations were performed by MALTS software 33 using the following parameters: an accelerating voltage of 300 kV, a mean inner potential of hcp Co of −29.6 V, and defocus values of −200 and +200 μm, which corresponded with the parameters of our LorTEM experiments. An induction map similar to the one from the electron hologram was simulated using an LLG micromagnetic simulator 34 .…”

Recent advances in Lorentz microscopy

“…al. implemented this approach to simulate LTEM images in an open-source software package called MALTS [21]; their software takes the output file from common micromagnetic simulation software packages, such as OOMMF or MuMax, as input. The LLG Micromagnetic simulator is the only other commercially available software capable of simulating LTEM images [22].…”