Summer Research Experience for Undergraduates 2023
2023 Summer REU Student Information & Research Abstracts
Name: Catherine Casbohm
Undergraduate Institution: Ohio State University
Major: Physics
REU Advisor: Chris Hammel
Project Title: Ferromagnetic Resonance on YG/NM Bilayers
Abstract: Understanding interfacial interactions in magnetic-insulators based heterostructures have generated significant interest because it opens the opportunity to control novel magnetics phases that can lead to attractive spintronics applications. Magnetic insulators, such as, Yttrium Iron Garnet (YIG) have been widely explored for different applications due to its extremely low magnetic damping and high degree of crystalline and magnetic ordering. In this work we perform Ferromagnetic resonance (FMR) measurements on YIG thin films and extract the magnetic parameters, such as resonance field, effective magnetization, and damping constant. Subsequently, we deposit a layer of a Nonmagnetic material (NM) on top of the YIG to determine the effect of the interfacial interactions on the magnetic properties, particularly their impact on the magnetic anisotropy of the YIG thin films.
Name: Christian Castruita
Undergraduate Institution: California State University, Long Beach
Major: Physics and Math
REU Advisor: Michael Peterson, Yuanming Lu
Project Title: Chern Insulators
Abstract: Numerical calculations of the Chern number of the Haldane model with periodic and twisted boundary conditions using the Python package QuSpin. The results are discussed as well as hw the methods can be applied to investigate more complex systems such as fractional Chern insulators.
Name: Nathan Kim 
Undergraduate Institution: California State University, Long Beach
Major: Physics
REU Advisor: Roland Kawakami
Project Title: Developing a Magnetic Circular Dichroism Measurement System
Abstract: The Magneto Optical Kerr Effect refers to the change in the Kerr Angle due to a change in angle when the polarized light is reflected off of magnetic materials. Similarly, Magnetic Circular Dichroism (MCD) measures the change in absorption between the right and left polarized light. Using these ideas, we can look at the properties of different PMA materials. An experimental setup can be upgraded in order to measure these magnetic signals by adding microscopy and more movement control over the system.
Name: Lara McHale 
Undergraduate Institution: Dennison University
Major: Physics
REU Advisor: Sasha Landsman, Jinwoo Hwang
Project Title: Linear and Non-Linear Responses at Metal/ Magnetic Insulator Interfaces
Abstract: Metal/magnetic insulator interfaces are pivotal in comprehending magnetic materials’ static and dynamic magnetic phases, thereby revealing the multifaceted manipulation of magnetic states in interface-centric systems.We delved into the equilibrium physics of these interfaces, employing a two-leg ladder model, which serves as a theoretical tool to understand electronic systems’ behavior at these interfaces. This model elucidated electron mobility and conductivity in the metallic layer, correlated effects due to electron-electron interactions in the insulating layer, and the intricate interplay between both layers. By simplifying the model to two interconnected metallic chains, we analytically discerned the system’s energy bands. Furthermore, we probed the swift and non-linear dynamics of these interfaces by examining varying emission mechanisms for ultrafast spectroscopy, and how the High Harmonic Generation (HHG) non-linear process can reveal materials’ high-order susceptibility. The broader implications of our research pave the way for technological breakthroughs, extending from spintronics devices to ultrafast magnetic memory storage. Name: Nestor Plascencia
Undergraduate Institution: California State University, Long Beach
Major: Physics
REU Advisor: Ezekiel Johnston-Halperin
Project Title: Observing the Magnetic Properties of the Thin-Film Organic Magnet: V[TCNE]x
Abstract: The study of quantum information has led many researchers to rely on low-loss magnetic materials that are also capable of operating at low temperatures. Because of these constraints, the ferrimagnetic material yttrium iron garnet (YIG) has been the main material choice for decades and continues to be used to this day. However, a magnetic material named vanadium tetracyanoethylene (V[TCNE].) shows promise of being an alternative to YIG due to its low damping properties at low temperatures. In this research project, we seek to further refine the process of creating V[TCNE). by structurally improving the machine that creates it and analyze how different materials affect V[TCNE], when used as methods for protecting it from the atmosphere. Doing so will help improve its viability to be used in microwave electronic devices and assist the ongoing research of quantum information
Name: Sebastian Ramirez Renta
Undergraduate Institution: University of Puerto Rico
Major: Computer Engineering
REU Advisor: Jinwoo Hwang
Project Title: Quantitative Determination of Epitaxial Strain and Lattice Distortion at LaCoO3/SRTIO3 Interface Using Scanning Transmission Electron Microscopy
Abstract: Scanning transmission electron microscopy (STEM) enables investigation of arrangement of individual atoms with atomic scale resolution and precision. We apply atomic scale STEM to LaCoO3 (LCO) thin films to investigate how the strain at the interface creates emergent magnetism which is not achievable in bulk materials. This investigation requires the precise positions of the atoms at the interface since magnetism can vary greatly depending on how the atoms and lattices are strained or distorted at the interface by the epitaxial strain. We obtain high resolution images of the interface between the LCO and SrTiO3 substrate, and use the Fiji software as well as the newly developed Java script to automatically detect the exact positions of the atoms from the STEM images with picometer precision. Our calculation shows the in-plane La-La distances as the measure of the epitaxial strain, out-of-plane La-La distances as the measure of Poisson’s Ratio, and the rotation of oxygen octahedra as the measure of lattice distortion at the interface. We show that the strain and distortion relax as a function of the distance from the interface. Our result provides a highly precise understanding of the atomic structure that is essential to understanding the emergent properties of the novel magnetic interfaces.
Name: Max Windl
Undergraduate Institution: Arizona State University
Major: Mechanical Engineering
REU Advisor: Jos Heremans
Project Title: Transport Measurements in BiSb Alloys and Bi/MnBi Composites
Abstract: In this work, we measured Nernst and Seebeck coefficients in Bi88Sb12 alloys as a function of magnetic field and temperature and compared it to measurements in Bi/MnBi composites. In these composites, ferromagnetic MnBi needles are grown by solid state transformation in a Bi matrix by in-field annealing, resulting in combined transverse thermopowers from both Nernst and spin-Seebeck effects in a thermal gradient without external magnetic field. The orientation and intensity of this internal field can be controlled during the annealing process. The figure of merit for the Bi/MnBi compound was found to be too low for it to be a suitable thermoelectric, most probably caused by the high thermal conductivity of the metallic MnBi particles inside the Bi matrix.
Name: Rosemary Wynnychenko 
Undergraduate Institution: Wellesley College
Major: Physics
REU Advisor: Ronaldo Valdés Aguilar
Project Title: Attenuated Total Reflection Terahertz Spectroscopy
Abstract: Terahertz Time Domain Spectroscopy is a method used to characterize a material’s interaction with electromagnetic radiation with frequencies in the terahertz range, located between microwave and mid infrared wavelengths. This experiment uses Terahertz Time Domain Spectroscopy with an attenuated total reflection setup to probe the surfaces of materials. In an attenuated total reflection setup, a sample is placed behind a prism, such that light can enter the prism, undergo total internal reflection on the side of the prism next to the sample, and then exit the prism. By measuring the reflected THz pulse with and without the presence of a sample, the frequencies absorbed by the sample can be recorded. This experiment studies silicon and a split ring array on silicon. The distance between the sample and the prism is also varied. The pulse shape changes as a function of the distance between the sample and the prism, and oscillations appear in the frequency domain when the sample is very close to the prism.