Layer-Dependent Electronic Structure and Magnetic Transition Evolution in Two-Dimensional Ferromagnetic van der Waals Films

Event Date:
2024-12-12T13:00:00
2024-12-12T14:00:00
Event Location:
AMPEL building, Room 311
Speaker:
Ryan Roemer, PhD candidate
Related Upcoming Events:
Grad Theses
Intended Audience:
Public
Local Contact:

Internal Defense for Ryan Roemer (rroemer@phas.ubc.ca)

Event Information:

Abstract:
In this work, we explore what happens to a magnet when it is to only a few layers of atoms thick. To do this we grow crystals of Fe$_3$GeTe$_2$ with a technique akin to atomic spray paint, which allows for the precise control of atomic ratios to approach a nearly perfect stoichiometry.

We first demonstrate the wafer-scale synthesis of high-quality, single-crystalline FGT films with precise control over layer thickness from 1 to 10 quintuple layers (QLs). With this layer control, we are able to perform transport measurements that reveal robust ferromagnetism across all layer numbers, with drastic thickness-dependent Curie temperatures evolution from 1-4 layers.

We then employ angle-resolved photoemission (ARPES) spectroscopy and density functional theory calculations, to map the evolution of the electronic band structure with increasing layer number, identifying emergent bands and quantifying the effects of interlayer coupling.

Carrier Density measurements are then performed for all thicknesses as a function of temperature and compared to the density of states near the Fermi energy observed in ARPES. Surprisingly we observe a constant normalized carrier density per QL at the Curie temperature across different thicknesses, suggesting a universal mechanism underlying the ferromagnetic transition. We then discuss the applicability of itinerant electron-dominated or mediated mechanisms for magnetism and the unique Fe site contributions.
:
In this work, we explore what happens to a magnet when it is to only a few layers of atoms thick. To do this we grow crystals of Fe$_3$GeTe$_2$ with a technique akin to atomic spray paint, which allows for the precise control of atomic ratios to approach a nearly perfect stoichiometry.

We first demonstrate the wafer-scale synthesis of high-quality, single-crystalline FGT films with precise control over layer thickness from 1 to 10 quintuple layers (QLs). With this layer control, we are able to perform transport measurements that reveal robust ferromagnetism across all layer numbers, with drastic thickness-dependent Curie temperatures evolution from 1-4 layers.

We then employ angle-resolved photoemission (ARPES) spectroscopy and density functional theory calculations, to map the evolution of the electronic band structure with increasing layer number, identifying emergent bands and quantifying the effects of interlayer coupling.

Carrier Density measurements are then performed for all thicknesses as a function of temperature and compared to the density of states near the Fermi energy observed in ARPES. Surprisingly we observe a constant normalized carrier density per QL at the Curie temperature across different thicknesses, suggesting a universal mechanism underlying the ferromagnetic transition. We then discuss the applicability of itinerant electron-dominated or mediated mechanisms for magnetism and the unique Fe site contributions.
 

Add to Calendar 2024-12-12T13:00:00 2024-12-12T14:00:00 Layer-Dependent Electronic Structure and Magnetic Transition Evolution in Two-Dimensional Ferromagnetic van der Waals Films Event Information: Abstract:In this work, we explore what happens to a magnet when it is to only a few layers of atoms thick. To do this we grow crystals of Fe$_3$GeTe$_2$ with a technique akin to atomic spray paint, which allows for the precise control of atomic ratios to approach a nearly perfect stoichiometry. We first demonstrate the wafer-scale synthesis of high-quality, single-crystalline FGT films with precise control over layer thickness from 1 to 10 quintuple layers (QLs). With this layer control, we are able to perform transport measurements that reveal robust ferromagnetism across all layer numbers, with drastic thickness-dependent Curie temperatures evolution from 1-4 layers. We then employ angle-resolved photoemission (ARPES) spectroscopy and density functional theory calculations, to map the evolution of the electronic band structure with increasing layer number, identifying emergent bands and quantifying the effects of interlayer coupling. Carrier Density measurements are then performed for all thicknesses as a function of temperature and compared to the density of states near the Fermi energy observed in ARPES. Surprisingly we observe a constant normalized carrier density per QL at the Curie temperature across different thicknesses, suggesting a universal mechanism underlying the ferromagnetic transition. We then discuss the applicability of itinerant electron-dominated or mediated mechanisms for magnetism and the unique Fe site contributions.:In this work, we explore what happens to a magnet when it is to only a few layers of atoms thick. To do this we grow crystals of Fe$_3$GeTe$_2$ with a technique akin to atomic spray paint, which allows for the precise control of atomic ratios to approach a nearly perfect stoichiometry. We first demonstrate the wafer-scale synthesis of high-quality, single-crystalline FGT films with precise control over layer thickness from 1 to 10 quintuple layers (QLs). With this layer control, we are able to perform transport measurements that reveal robust ferromagnetism across all layer numbers, with drastic thickness-dependent Curie temperatures evolution from 1-4 layers. We then employ angle-resolved photoemission (ARPES) spectroscopy and density functional theory calculations, to map the evolution of the electronic band structure with increasing layer number, identifying emergent bands and quantifying the effects of interlayer coupling. Carrier Density measurements are then performed for all thicknesses as a function of temperature and compared to the density of states near the Fermi energy observed in ARPES. Surprisingly we observe a constant normalized carrier density per QL at the Curie temperature across different thicknesses, suggesting a universal mechanism underlying the ferromagnetic transition. We then discuss the applicability of itinerant electron-dominated or mediated mechanisms for magnetism and the unique Fe site contributions.  Event Location: AMPEL building, Room 311