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  4. Studies In Nanomagnetism: Co/Ni Multilayers In Magnetic Tunnel Junctions, Nanomagnets In Superconducting Microwave Cavities, And Magnetic Multilayer Nanowires

Studies In Nanomagnetism: Co/Ni Multilayers In Magnetic Tunnel Junctions, Nanomagnets In Superconducting Microwave Cavities, And Magnetic Multilayer Nanowires

File(s)
tjg63.pdf (14.55 MB)
Permanent Link(s)
https://hdl.handle.net/1813/36034
Collections
Cornell Theses and Dissertations
Author
Gudmundsen, Theodore
Abstract

Three experiments in nanomagnetism were performed. In the first, we reduced the switching current of a magnetic tunnel junction by incorporating Co/Ni films possessing perpendicular magnetic anisotropy (PMA). We characterized Co/Ni films with vibrating sample magnetometry and ferromagnetic resonance and measured a PMA of 0.22-0.26 mJ/m2 . By combining Co/Ni films with FeCoB in the electrodes, we reduced the demagnetization field of the free layer from 13000 Oe to 2000 Oe, while maintaining a low damping of only .015. These [Co/Ni]/FeCoB devices had 106% TMR at maximum, and 38% in a device with resistance below 10 Ω-um2 that was spin-torque switchable. We demonstrated spin-torque switching in magnetic tunnel junctions of this kind, and saw some reduction of the switching current compared to similar devices in the literature. In the second project, I endeavored to design a niobium superconducting microwave cavity that I could strongly couple to a nanomagnet for a variety of scientific and technological applications. Towards that end, I successfully designed, fabricated, and packaged a 50 ohm superconducting cavity in the coplanar waveguide geometry with an unprecedently thin center line of 476 nm. Under cryogenic conditions, the cavity showed a quality factor of 566 at 5.9 GHz. In the third project, I designed an electrically switchable three-terminal device for injecting spin currents into semiconductors. The device consists of a multilayer magnetic nanowire with a domain wall that can be moved by spin-torque transfer. I designed a fabrication recipe to make that device, and made significant progress towards fabricating a complete device, including the demonstration of the lithography for all four layers.

Date Issued
2014-01-27
Keywords
Nanomagnetics
•
MRAM
•
Magnetism
Committee Chair
Ralph, Daniel C
Committee Member
Arias, Tomas A.
Buhrman, Robert A
Degree Discipline
Physics
Degree Name
M.S., Physics
Degree Level
Master of Science
Type
dissertation or thesis

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