Date of Award
12-1-2024
Degree Name
Doctor of Philosophy
Department
Physics, Applied
First Advisor
Mazumdar, Dipanjan
Abstract
The incredible progress of the microelectronics industry in the last several decades hasbeen primarily due to the progressive miniaturization and optimization of the MOSFET. However, the rate of this progress is becoming unsustainable by these means. Of several proposed replacements, one of the most popular ideas is to utilize electronic spin in logical processing. The discovery of Giant Magntoresistance (GMR) in layered thin film heterostructures and the subsequent development of Tunneling Magnetoresistance (TMR) devices revolutionized magnetic field sensing, which allowed magnetic domains in hard drives to get much smaller. This enabled hard drives to get denser, but because current charge-based devices are still much faster and smaller and require less energy to switch than magnetic domains, charge-based devices are still preferred for primary storage (RAM). The discoveries of Spin Orbit Torque (SOT) and Spin Transfer Torque (STT) have demonstrated that spin can be utilized for writing as well due to interactions between spin and the magnetization of a ferromagnet. Although magnetoresistive RAM (MRAM) has already been successfully implemented as a commercially available product, it remains small and expensive and is only used in specific applications. This is partially due to limitations of the individual constituent materials as spin filters or conductors, and partially due to incompatibility of adjacent crystal layers in a heterostructure. Many different types of mai terials have recently been identified as promising candidates for an optimized spin-based device. Manganese-based Heusler compounds constitute a large subset of these theoretically predicted materials due to their high perpendicular magnetic anisotropy (PMA), high curie temperatures, and low saturation fields, as well as their spin conduction, all with very similar crystal structures. In this work, I study magnetotransport and magneto-optical properties of Mn2FeSn and Fe2MnSn thin films and review properties of their parent compound Mn3Sn, which has been reported on extensively in the literature. My experimental methods involved a combination of homemade setups and sophisticated commercial tools. I may have observed a large topological Hall effect in a D019 Mn2FeSn thin film, and did observe a major substrate dependence on the properties of D019 Fe2MnSn thin films and a curious current dependence on the magnetoresistance behaviour in an Fe2MnSn thin film. This work emphasizes the sensitivity of Heusler alloy stoichiometry.
Access
This dissertation is Open Access and may be downloaded by anyone.