Microstructural Analysis of Garnet-Heavy Metal Heterostructures

Rare earth iron garnets (REIGs) are a class of ferrimagnetic insulators desirable for their tunable magnetic properties. Saturation magnetization, perpendicular magnetic anisotropy (PMA), coercivity, and Gilbert damping are just a few characteristics that can be altered via elemental substitution or strain on the film [1,2]. These adjustable features make REIGs desirable magnetic materials for spintronics [3]. Spintronics devices aim to provide CMOS compatible microelectronics that utilize electric charge and magnetic moments to store and process information. REIGs exhibit a variety of magnetic interactions, both bulk and interfacial, which are valuable for spintronics. Interfacial phenomena such as spin transfer torque, spin orbit torque, and interfacial Dzyaloshinskii-Moriya interaction have all been clearly observed in REIG-heavy metal heterostructures [4,5]. These specific events allow the magnetization of the REIG to be switched without the use of an external magnetic field at very low powers. Their fast switching is showcased in ultrafast domain wall velocities reported in Bi-substituted yttrium iron garnet and thullium iron garnet [6]. Plus, their high magnetooptical behavior allows REIGs to be studied via light techniques such as magnetooptical Kerr effect imaging and Brillouin light scattering [7]. While these magnetic interactions show promise for REIGs in spintronics applications, integrating these materials on Si requires further microstructure analysis. Polycrystalline dyprosium iron garnet (DyIG) has been successfully grown on Si with PMA due to an external rapid thermal anneal after pulsed laser deposition [8]. However, crystallization is limited to thicknesses above 20 nm. Furthermore, Pt is often used as a heavy metal for investigating interfacial phenomena in REIGs [9,10,11]. However, the REIG film growth is a kinetically active, high temperature, and oxygen rich environment. Pt durability during this process has yet to be studied. This thesis involves designing, building, and characterizing a heterostructure to achieve 10 nm thin DyIG and Y substituted DyIG on Si. A paramagnetic garnet, gadolinium gallium garnet, is used as a templating layer for the REIG, and a thin Pt diffusion barrier is sputtered between the two garnet layers. Microstructural and magnetic characteristics are investigated.

Name thesis:degree_name

Master

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2023

Author dc:creator

• Gross, Miela Josephine

Advisor dc:contributor.advisor

• Ross, Caroline A.

Statement dc:rights

• In Copyright - Educational Use Permitted
• Copyright MIT

Licence dc:rights.uri

• http://rightsstatements.org/page/InC-EDU/1.0/

Handle dc:identifier.uri

https://hdl.handle.net/1721.1/150294

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/150294