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Two-dimensional Fe3GeTe2: strain effect on magneto-crystalline anisotropy

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Abstract
In recent years, two-dimensional (2D) materials have attracted growing attention. Atomically
thin materials exhibit remarkably different properties from bulk. According to Mermin-WagnerHohenberg theorem, no long-range magnetic order is possible in 2D. However, magnetism in 2D has
been recently observed experimentally such as CrI3, Cr2Ge2Te6 and Fe3GeTe2. Fe3GeTe2 has relatively
higher curie temperature ~130 K than other 2D materials. In this dissertation, we studied monolayer
and bilayer Fe3GeTe2, more specifically strain (−5 % ≤ η ≤ 5 %) effect on magnetic properties.
1. Monolayer Fe3GeTe2: Strain dependence of magnetism is revealed. Among two Fe sites,
Fe1 shows greater change of magnetic moments more than Fe2, from 1.53 𝜇𝐵 at −5 %
to 2.37 𝜇𝐵 at +5 % of strain. Density of states of Fe1 are compared for each strain,
different magnetic moments are associated with different peak feature. Furthermore,
magneto-crystalline anisotropy (MCA) is investigated, where monolayer Fe3GeTe2
prefers perpendicular magnetization for all strains. MCA energy changes with respect to
strain, where minimum value is 0.85 meV at η = −5 %, maximum value is 4.72 meV
without strain. Band structures at η = −5 % and 0 % are compared to analyze MCA of
two strains.
2. Bilayer Fe3GeTe2: With ferromagnetic monolayer, bilayer Fe3GeTe2 energetically
prefers antiferromagnetic state without strain. Transition to ferromagnetic state occurs at
η = +4.16 %. Besides, at compressive strain, buckling happens in Fe2-Ge plane, which
results in different magnetic moments of Fe1(in) and Fe1(out). Density of states of Fe1
are investigated to study strain dependence of magnetic moments.
Author(s)
김경혜
Issued Date
2021
Awarded Date
2021-02
Type
Dissertation
URI
https://oak.ulsan.ac.kr/handle/2021.oak/5689
http://ulsan.dcollection.net/common/orgView/200000373412
Affiliation
울산대학교
Department
일반대학원 물리학과
Advisor
임성현
Degree
Master
Publisher
울산대학교 일반대학원 물리학과
Language
eng
Appears in Collections:
Physics > 1. Theses (Master)
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