Quantitative study of magnetic field distribution by electron holography and micromagnetic simulations

Beleggia, Marco; Schofield, M. A.; Zhu, Yu; Malac, Marek; Liu, Z.; Freeman, Michael W.

doi:10.1063/1.1603355

Cited by 24 publications

(11 citation statements)

References 14 publications

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“…The resultant spin-vector distributions of two magnetic layers were then utilized to numerically calculate the projected electron phase shift, using the Fourier-transform based method developed by Beleggia and Zhu. [15] The measured values agree well with the calculations in both the distribution profile and the peak amplitude. More importantly, this directly confirms the feasibility of using defined field sequences to generate specific double-vortex states in a fully controllable manner.…”

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confidence: 79%

Control of Double‐Vortex Domain Configurations in a Shape‐Engineered Trilayer Nanomagnet System

2010

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Intense interest in nanomagnetic materials is stimulated by the continuing quest for smaller, faster, and more energy efficient magnetic devices. [1,2] Rapid miniaturization has pushed the physical dimensions of magnetic devices into the submicrometer region, where new and intriguing size-dependent phenomena take effect. [3][4][5] At this length scale, the exchange and magnetostatic energies are of comparable magnitude and small variations of size or shape in the nanomagnetic system dramatically alters the energy levels and ground-state spin configuration. Moreover, to achieve specific functionality, especially with multicomponent devices, the overall magnetization process must be precisely engineered to ensure reliable operation. [6,7] Accordingly, the ability to effectively probe and analyze complex multilayer spin configurations and magnetization processes plays a key role in the development of next-generation magnetic nanotechnologies.[8]Here, we focus on a novel nanometric trilayer structure consisting of two shape-engineered permalloy (Py, Ni 80 Fe 20 ) layers separated by a nonmagnetic aluminum (Al) spacer, as a model experimental system. Using electron holography techniques, as described in the Experimental section, we directly characterize the magnetization reversal behavior of individual trilayer stacks and show that separate chirality-controlled vortex nucleation and annihilation events in the two magnetic layers are responsible for the underlying reversal mechanism. Accordingly, we exploit this reversal behavior to systematically obtain four distinct configurations of flux-closure, double-vortex states at remanence that are controllably generated by applying defined magnetic-field sequences to individual nanomagnetic trilayer stacks.The flux-closure state is attractive in device application to minimize undesired interaction between neighboring nanomagnets.[9] Specifically, the magnetic vortex state is characterized by a planar curling of the magnetic spin configuration with a specific chirality (either clockwise (CW) or counter-clockwise (CCW)) around a nanometer-sized vortex region, wherein the magnetization achieves an out-of-plane spin polarity.[10] The magnetic vortex state is acquired (through nucleation) in the ground-state remanent configuration, for nanomagnets within a certain range of aspect ratios for the characteristic planar dimension and thickness.[11] Here, we combine a semi-square and semi-disk planar shape to control the vortex chirality upon nucleation as illustrated by micromagnetic simulations for a single-layer structure (Fig.

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confidence: 79%

Control of Double‐Vortex Domain Configurations in a Shape‐Engineered Trilayer Nanomagnet System

2010

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“…To enable comparisons with differential phase contrast (DPC) measurements (discussed later), we display in the middle column of Figure 2 the calculated integrated induction field components in the plane of the sample that would be imaged in the experiment, using the Fourier space approach to solving the Aharonov-Bohm equation. 16 With the electron beam travelling along a path perpendicular to the film, DPC is insensitive to the zcomponent of the magnetisation. The projected inplane magnetisation and induction will differ if the magnetisation has any divergence.…”

Section: Numerical Simulation Of Chiral Soliton Lattice Dislocationsmentioning

confidence: 99%

Order and disorder in the magnetization of the chiral crystal CrNb3S6

et al. 2019

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Competing magnetic anisotropies in chiral crystals with Dzyaloshinskii Moriya exchange interactions can give rise to non-trivial chiral topological magnetisation configurations with new and interesting properties. One such configuration is the magnetic soliton, where the moment continuously rotates about an axis. This magnetic system can be considered to be one dimensional and, because of this, it supports a macroscale coherent magnetisation, giving rise to a tunable chiral soliton lattice (CSL) that is of potential use in a number of applications in nanomagnetism and spintronics. In this work we characterise the transitions between the forced-ferromagnetic (F-FM) phase and the CSL one in CrNb 3 S 6 using differential phase contrast imaging in a scanning transmission electron microscope, conventional Fresnel imaging, ferro-magnetic resonance spectroscopy, and mean-field modelling. We find that the formation and movement of dislocations mediate the formation of CSL and F-FM regions and that these strongly influence the highly hysteretic static and dynamic properties of the system. Sample size and morphology can be used to tailor the properties of the system and, with the application of magnetic field, to locate and stabalise normally unstable dislocations and modify their dimensions and magnetic configurations in ways beyond that predicted to occur in uniform films. KeywordsChiral soliton lattice, CrNb 3 S 6 , dislocation, differential phase contrast, transmission electron microscopy, Lorentz microscopy, Fresnel microscopy, ferromagnetic resonance spectroscopy 1 arXiv:1903.09519v1 [cond-mat.mtrl-sci]

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“…Assuming that the x-and y-components of magnetisation vary only with the x-and y-coordinates, the magnetic phase component can be simplified in reciprocal space [21] to This assumption holds over a single mesh in the z direction. MALTS deals with multiple meshes in the z direction via the linear addition of magnetic phases accrued through each individual mesh.…”

Section: Fig 1 Herementioning

confidence: 99%

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

et al. 2013

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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.

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Quantitative study of magnetic field distribution by electron holography and micromagnetic simulations

Cited by 24 publications

References 14 publications

Control of Double‐Vortex Domain Configurations in a Shape‐Engineered Trilayer Nanomagnet System

Control of Double‐Vortex Domain Configurations in a Shape‐Engineered Trilayer Nanomagnet System

Order and disorder in the magnetization of the chiral crystal CrNb3S6

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

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