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Title: Determination of domain wall chirality using in situ Lorentz transmission electron microscopy

Abstract

Controlling domain wall chirality is increasingly seen in non-centrosymmetric materials. Mapping chiral magnetic domains requires knowledge about all the vector components of the magnetization, which poses a problem for conventional Lorentz transmission electron microscopy (LTEM) that is only sensitive to magnetic fields perpendicular to the electron beams direction of travel. The standard approach in LTEM for determining the third component of the magnetization is to tilt the sample to some angle and record a second image. Furthermore, this presents a problem for any domain structures that are stabilized by an applied external magnetic field (e.g. skyrmions), because the standard LTEM setup does not allow independent control of the angle of an applied magnetic field, and sample tilt angle. Here we show that applying a modified transport of intensity equation analysis to LTEM images collected during an applied field sweep, we can determine the domain wall chirality of labyrinth domains in a perpendicularly magnetized material, avoiding the need to tilt the sample.

Authors:
 [1];  [2];  [2];  [1]
  1. Univ. of Oregon, Eugene, OR (United States)
  2. Univ. of California, San Diego, CA (United States); Univ. of California, San Diego, La Jolla, CA (United States)
Publication Date:
Research Org.:
Univ. of Oregon, Eugene, OR (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1349368
Alternate Identifier(s):
OSTI ID: 1393529; OSTI ID: 1421279
Grant/Contract Number:
SC0010466; SC0003678
Resource Type:
Journal Article: Published Article
Journal Name:
AIP Advances
Additional Journal Information:
Journal Volume: 7; Journal Issue: 5; Journal ID: ISSN 2158-3226
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Domain walls; Chiral symmetries; Magnetic fields; Magnetic induction; Nucleation

Citation Formats

Chess, Jordan J., Montoya, Sergio A., Fullerton, Eric E., and McMorran, Benjamin J.. Determination of domain wall chirality using in situ Lorentz transmission electron microscopy. United States: N. p., 2017. Web. doi:10.1063/1.4977500.
Chess, Jordan J., Montoya, Sergio A., Fullerton, Eric E., & McMorran, Benjamin J.. Determination of domain wall chirality using in situ Lorentz transmission electron microscopy. United States. doi:10.1063/1.4977500.
Chess, Jordan J., Montoya, Sergio A., Fullerton, Eric E., and McMorran, Benjamin J.. Thu . "Determination of domain wall chirality using in situ Lorentz transmission electron microscopy". United States. doi:10.1063/1.4977500.
@article{osti_1349368,
title = {Determination of domain wall chirality using in situ Lorentz transmission electron microscopy},
author = {Chess, Jordan J. and Montoya, Sergio A. and Fullerton, Eric E. and McMorran, Benjamin J.},
abstractNote = {Controlling domain wall chirality is increasingly seen in non-centrosymmetric materials. Mapping chiral magnetic domains requires knowledge about all the vector components of the magnetization, which poses a problem for conventional Lorentz transmission electron microscopy (LTEM) that is only sensitive to magnetic fields perpendicular to the electron beams direction of travel. The standard approach in LTEM for determining the third component of the magnetization is to tilt the sample to some angle and record a second image. Furthermore, this presents a problem for any domain structures that are stabilized by an applied external magnetic field (e.g. skyrmions), because the standard LTEM setup does not allow independent control of the angle of an applied magnetic field, and sample tilt angle. Here we show that applying a modified transport of intensity equation analysis to LTEM images collected during an applied field sweep, we can determine the domain wall chirality of labyrinth domains in a perpendicularly magnetized material, avoiding the need to tilt the sample.},
doi = {10.1063/1.4977500},
journal = {AIP Advances},
number = 5,
volume = 7,
place = {United States},
year = {Thu Feb 23 00:00:00 EST 2017},
month = {Thu Feb 23 00:00:00 EST 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1063/1.4977500

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  • Controlling domain wall chirality is increasingly seen in non-centrosymmetric materials. Mapping chiral magnetic domains requires knowledge about all the vector components of the magnetization, which poses a problem for conventional Lorentz transmission electron microscopy (LTEM) that is only sensitive to magnetic fields perpendicular to the electron beams direction of travel. The standard approach in LTEM for determining the third component of the magnetization is to tilt the sample to some angle and record a second image. Furthermore, this presents a problem for any domain structures that are stabilized by an applied external magnetic field (e.g. skyrmions), because the standard LTEMmore » setup does not allow independent control of the angle of an applied magnetic field, and sample tilt angle. Here we show that applying a modified transport of intensity equation analysis to LTEM images collected during an applied field sweep, we can determine the domain wall chirality of labyrinth domains in a perpendicularly magnetized material, avoiding the need to tilt the sample.« less
  • Direct observation of domain wall (DW) nucleation and propagation in focused electron beam induced deposited Co nanowires as a function of their dimensions was carried out by Lorentz microscopy (LTEM) upon in situ application of magnetic field. Optimal dimensions favoring the unambiguous DW nucleation/propagation required for applications were found in 500-nm-wide and 13-nm-thick Co nanowires, with a maximum nucleation field and the largest gap between nucleation and propagation fields. The internal DW structures were resolved using the transport-of-intensity equation formalism in LTEM images and showed that the optimal nanowire dimensions correspond to the crossover between the nucleation of transverse andmore » vortex walls.« less
  • In situ investigations of rapid solidification in polycrystalline Al thin films were conducted using nano-scale spatio-temporal resolution dynamic transmission electron microscopy. Differences in crystal growth rates and asymmetries in melt pool development were observed as the heat extraction geometry was varied by controlling the proximity of the laser-pulse irradiation and the associated induced melt pools to the edge of the transmission electron microscopy support grid, which acts as a large heat sink. Experimental parameters have been established to maximize the reproducibility of the material response to the laser-pulse-related heating and to ensure that observations of the dynamical behavior of themore » metal are free from artifacts, leading to accurate interpretations and quantifiable measurements with improved precision. Interface migration rate measurements revealed solidification velocities that increased consistently from ~1.3 m s –1 to ~2.5 m s –1 during the rapid solidification process of the Al thin films. Under the influence of an additional large heat sink, increased crystal growth rates as high as 3.3 m s –1 have been measured. The in situ experiments also provided evidence for development of a partially melted, two-phase region prior to the onset of rapid solidification facilitated crystal growth. As a result, using the experimental observations and associated measurements as benchmarks, finite-element modeling based calculations of the melt pool evolution after pulsed laser irradiation have been performed to obtain estimates of the temperature evolution in the thin films.« less