Towards sub-nanometer real-space observation of spin and orbital magnetism at the Fe/MgO interface

Thersleff, Thomas; Muto, Shunsuke; Werwiński, Mirosław; Spiegelberg, Jakob; Kvashnin, Yaroslav; Hjörvarsson, Bjørgvin; Eriksson, Olle; Rusz, Ján; Leifer, Klaus

doi:10.1038/srep44802

Cited by 17 publications

(17 citation statements)

References 40 publications

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“…The spin and orbital moments and magnetocrystalline anisotropy constants are presented as functions of the atomic position or angle. 21,33,64 The magnetocrystalline anisotropy energy (MAE) is one of the most important intrinsic properties of the hard magnetic crystals which can be analyzed in reciprocal space as a k-resolved quantity. The MAE can be determined with the magnetic force theorem 29,65,66 from a formula: (10) where ǫ i is the band energy of the ith state and θ is the angle between the magnetization direction and the c axis.…”

Section: G Mae Analysis In Reciprocal Spacementioning

confidence: 99%

Ab initiostudy of magnetocrystalline anisotropy, magnetostriction, and Fermi surface of L1₀FeNi (tetrataenite)

Werwiński¹,

Marciniak²

2017

J. Phys. D: Appl. Phys.

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The ordered L1 0 FeNi phase (tetrataenite) is recently considered as a promising candidate for the rare-earth free permanent magnets applications. In this work we calculate several characteristics of the L1 0 FeNi, where most of the results come form the fully relativistic full potential FPLO method with the generalized gradient approximation (GGA). A special attention deserves the summary of the magnetocrystalline anisotropy energies (MAE's), the full potential calculations of the anisotropy constant K 3 , and the combined analysis of the Fermi surface and three-dimensional k-resolved MAE. Other calculated parameters presented in this article are the magnetic moments ms and m l , magnetostrictive coefficient λ 001 , bulk modulus B 0 , and lattice parameters. The MAE's summary shows rather big discrepancies between the experimental MAE's from literature and also between the calculated MAE's. The MAE's calculated in this work with the full potential and GGA are equal to 0.47 MJ m −3 from WIEN2k, 0.34 MJ m −3 from FPLO, and 0.23 MJ m −3 from FP-SPR-KKR code. These last results strongly suggest that the value of MAE in GGA is below 0.5 MJ m −3 . It is also expected that this value is significantly underestimated due to the limitations of the GGA. Unfortunately, as other authors suggest, even the MAE equal 1.3 MJ m −3 would be insufficient to raise the L1 0 FeNi from the category of semi-hard magnets. However the L1 0 FeNi has still a potential to improve its MAE by modifications, like e.g. tetragonal strain or alloying. The presented three-dimensional k-resolved map of the MAE combined with the Fermi surface gives a complete picture of the MAE contributions in the Brillouin zone. The calculated Fermi surface consists of closed hole pockets and open sheets. It reflects a four-fold symmetry of the crystal and is closely related to the MAE(k). The analysis of the effects of external factors, like strain, on the k-resolved MAE and Fermi surface should be beneficial in engineering of the hard magnetic properties. The obtained from full potential FP-SPR-KKR method magnetocrystalline anisotropy constants K 2 and K 3 are several orders of magnitude smaller than the MAE/K 1 and equal to -2.0 kJ m −3 and 110 J m −3 , respectively. The calculated partial spin and orbital magnetic moments of the L1 0 FeNi are equal to 2.72 and 0.054 µ B for Fe and 0.53 and 0.039 µ B for Ni atoms, respectively. The calculations of geometry optimization lead to a c/a ratio equal to 1.0036, B 0 equal to 194 GPa, and λ 001 equal to 9.4 × 10 −6 .

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Section: G Mae Analysis In Reciprocal Spacementioning

confidence: 99%

Ab initiostudy of magnetocrystalline anisotropy, magnetostriction, and Fermi surface of L1₀FeNi (tetrataenite)

Werwiński¹,

Marciniak²

2017

J. Phys. D: Appl. Phys.

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“…The EMCD technique was proposed in 2003 [3] and experimentally demonstrated in 2006 [4]. From the time of its discovery, EMCD has seen a continuous rise and researchers have put serious efforts to improve the signal to noise (S/N) ratio [5][6][7][8][9] and the spatial resolution [10][11][12][13][14][15] of the technique. This led the EMCD technique to explore many materials based problems [16][17][18][19][20][21] as well as to obtain the magnetic signals from single atomic planes [22,23].…”

Section: Introductionmentioning

confidence: 99%

“…From the time of its discovery, EMCD has seen a continuous improvement in the signal to noise (S/N) ratio [5][6][7][8][9][10] , the spatial resolution [11][12][13][14][15][16] and the quantitative analysis. The technique has also been applied to explore material based questions such as interfacial magnetism 17,18 , magnetocrystalline anisotropy 19 , properties of dilute magnetic semiconductors 20 and rare earth magnets 21 . Recently EMCD signals with single atomic plane resolution were achieved 22,23 .…”

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Simultaneous mapping of EMCD signals and crystal orientations in a transmission electron microscope

Ali

Rusz

Warnatz

et al. 2021

Sci Rep

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When magnetic properties are analysed in a transmission electron microscope using the technique of electron magnetic circular dichroism (EMCD), one of the critical parameters is the sample orientation. Since small orientation changes can have a strong impact on the measurement of the EMCD signal and such measurements need two separate measurements of conjugate EELS spectra, it is experimentally non-trivial to measure the EMCD signal as a function of sample orientation. Here, we have developed a methodology to simultaneously map the quantitative EMCD signals and the local orientation of the crystal. We analyse, both experimentally and by simulations, how the measured magnetic signals evolve with a change in the crystal tilt. Based on this analysis, we establish an accurate relationship between the crystal orientations and the EMCD signals. Our results demonstrate that a small variation in crystal tilt can significantly alter the strength of the EMCD signal. From an optimisation of the crystal orientation, we obtain quantitative EMCD measurements.

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“…The down side of the TEM and also, to some extent of the XMCD measurements are the very weak signal strength. During the last decade, various experimental acquisition geometries were proposed and shown to obtain an EMCD signal such as energy filtered diffraction patterns [5], energy filtered images [6] [7] [8] and using convergent electron beams [9] [10]. A major effort has been to demonstrate magnetic information from EMCD experiments down to single atomic plane resolution [11] [12].…”

Section: Introductionmentioning

confidence: 99%

Quantitative EMCD by use of a double aperture for simultaneous acquisition of EELS

et al. 2019

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The weak signal strength in electron magnetic circular dichroism (EMCD) measurements remains one of the main challenges in the quantification of EMCD related EELS spectra. As a consequence, small variations in peak intensity caused by changes of background intervals, choice of method for extraction of signal intensity and equally differences in sample quality can cause strong changes in the EMCD signal. When aiming for high resolution quantitative EMCD, an additional difficulty consists in the fact that the two angular resolved EELS spectra needed to obtain the EMCD signal are taken at two different instances and it cannot be guaranteed that the acquisition conditions for these two spectra are identical. Here, we present an experimental setup where we use a double hole aperture in the transmission electron microscope to obtain the EMCD signal in a single acquisition. This geometry allows for the parallel acquisition of the two electron energy loss spectra (EELS) under exactly the same conditions. We also compare the double aperture acquisition mode with the qE acquisition mode which has been previously used for parallel acquisition of EMCD. We show that the double aperture mode not only offers better signal to noise ratio as compared to qE mode but also allows for much higher acquisition times to significantly improve the signal quality which is crucial for quantitative analysis of the magnetic moments.

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Towards sub-nanometer real-space observation of spin and orbital magnetism at the Fe/MgO interface

Cited by 17 publications

References 40 publications

Ab initiostudy of magnetocrystalline anisotropy, magnetostriction, and Fermi surface of L1₀FeNi (tetrataenite)

Ab initiostudy of magnetocrystalline anisotropy, magnetostriction, and Fermi surface of L1₀FeNi (tetrataenite)

Simultaneous mapping of EMCD signals and crystal orientations in a transmission electron microscope

Quantitative EMCD by use of a double aperture for simultaneous acquisition of EELS

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Towards sub-nanometer real-space observation of spin and orbital magnetism at the Fe/MgO interface

Cited by 17 publications

References 40 publications

Ab initiostudy of magnetocrystalline anisotropy, magnetostriction, and Fermi surface of L10FeNi (tetrataenite)

Ab initiostudy of magnetocrystalline anisotropy, magnetostriction, and Fermi surface of L10FeNi (tetrataenite)

Simultaneous mapping of EMCD signals and crystal orientations in a transmission electron microscope

Quantitative EMCD by use of a double aperture for simultaneous acquisition of EELS

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Product

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Ab initiostudy of magnetocrystalline anisotropy, magnetostriction, and Fermi surface of L1₀FeNi (tetrataenite)

Ab initiostudy of magnetocrystalline anisotropy, magnetostriction, and Fermi surface of L1₀FeNi (tetrataenite)