Tyler Reichanadter

EECS Department, University of California, Berkeley

Technical Report No. UCB/

May 1, 2025

The gradual waning of Moore’s law for charge-based information media scaling has intensified in- terest in spin-based information platforms, where the electronic spin degree of freedom is harnessed for energy-efficient logic and memory. State-of-the-art spintronic memory and logic architectures utilize intricate magnetic textures that are emergent only in the low-dimensional limit and at atomically precise interfaces, motivating a deep interest in layered magnetic materials that pre- serve robust magnetic order. Such designs rely on a precise understanding of how the atomic-scale structure dictates magnetic interactions in these low-dimensional and layered materials, a challenge well-suited to first-principles electronic-structure theory.

This dissertation presents several density functional theory (DFT) studies that reveal how dop- ing, intercalation, and structural tuning govern emergent magnetism in layered magnetic mate- rials. These studies span primarily two material systems, Fe5−xGeTe2 and Fex-NbS2 , which both support chemical doping that greatly influence their electronic and magnetic order. The pri- mary investigations consist of: (i) the evolution of exchange interactions that stabilize a skyrmion lattice in Co-doped (CoxFe1−x)5GeTe2, (ii) the enhancement of the Curie temperature in Ni- doped Fe5+xGeTe2 and its microscopic origin, and (iii) the sharp electronic reconstruction in Fe-intercalated Fex-NbS2 across the critical doping boundary xc = 1/3, which coincides with an antiferromagnetic phase transition. In all cases, the primary focus is in utilizing ground state ionic structure, electronic structure, and local magnetic moment calculations, along with pure spatial analysis and symmetry considerations to identify fundamental mechanism driving the morphotropic phase transitions in these compounds. Many of these doped magnetic structures preserve some de- gree of single-crystal order that are readily modeled using atomic supercells, motivating electronic structure unfolding schemes that enhance the chemical bonding analysis in these intermediate- doping-regime motifs. Together, these studies highlight how chemical and structural control can engineer nontrivial magnetic ordering and textures in atomically thin systems.

Advisors: Jeffrey Bokor

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BibTeX citation:

@phdthesis{Reichanadter:32001,
    Author= {Reichanadter, Tyler},
    Title= {First principles studies of emergent magnetism in layered and disordered quantum materials},
    School= {EECS Department, University of California, Berkeley},
    Year= {2025},
    Month= {Dec},
    Number= {UCB/},
    Abstract= {The gradual waning of Moore’s law for charge-based information media scaling has intensified in-
terest in spin-based information platforms, where the electronic spin degree of freedom is harnessed
for energy-efficient logic and memory. State-of-the-art spintronic memory and logic architectures
utilize intricate magnetic textures that are emergent only in the low-dimensional limit and at
atomically precise interfaces, motivating a deep interest in layered magnetic materials that pre-
serve robust magnetic order. Such designs rely on a precise understanding of how the atomic-scale
structure dictates magnetic interactions in these low-dimensional and layered materials, a challenge
well-suited to first-principles electronic-structure theory.

This dissertation presents several density functional theory (DFT) studies that reveal how dop-
ing, intercalation, and structural tuning govern emergent magnetism in layered magnetic mate-
rials. These studies span primarily two material systems, Fe5−xGeTe2 and Fex-NbS2 , which
both support chemical doping that greatly influence their electronic and magnetic order. The pri-
mary investigations consist of: (i) the evolution of exchange interactions that stabilize a skyrmion
lattice in Co-doped (CoxFe1−x)5GeTe2, (ii) the enhancement of the Curie temperature in Ni-
doped Fe5+xGeTe2 and its microscopic origin, and (iii) the sharp electronic reconstruction in
Fe-intercalated Fex-NbS2 across the critical doping boundary xc = 1/3, which coincides with an
antiferromagnetic phase transition. In all cases, the primary focus is in utilizing ground state ionic
structure, electronic structure, and local magnetic moment calculations, along with pure spatial
analysis and symmetry considerations to identify fundamental mechanism driving the morphotropic
phase transitions in these compounds. Many of these doped magnetic structures preserve some de-
gree of single-crystal order that are readily modeled using atomic supercells, motivating electronic
structure unfolding schemes that enhance the chemical bonding analysis in these intermediate-
doping-regime motifs. Together, these studies highlight how chemical and structural control can
engineer nontrivial magnetic ordering and textures in atomically thin systems.},
}

EndNote citation:

%0 Thesis
%A Reichanadter, Tyler 
%T First principles studies of emergent magnetism in layered and disordered quantum materials
%I EECS Department, University of California, Berkeley
%D 2025
%8 May 1
%@ UCB/
%F Reichanadter:32001