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Title: Manipulation of fullerene C60 spintronic devices via ferromagnetic resonance
Author: Wheeler, May Catherine
ISNI:       0000 0004 5346 7229
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2014
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C60 has been included in hybrid magneto-molecular devices as an active layer where the C60 is thermally sublimated under high vacuum and the metals are sputter deposited in-situ. Multilayer C60/Co samples were measured by x-ray reflectivity and transmission electron microscopy to show that there is little interdiffusion of layers suggesting C60 is robust to the deposition of metals by sputtering. We have observed 25% magnetoresistance through 60 nm of C60 at 10 K as well as 8% magnetoresistance at room temperature through 20 nm of C60. Unexpected asymmetric effects in external magnetic field were observed in some C60 spin valves as a result of interfacial hybridisation between C60 and ferromagnetic materials. It has also been shown that when C60 is in contact with a ferromagnetic material, spin polarised electrons from the ferromagnet are transferred into the C60 as a result of differences in chemical potential. This has been measured in C60/Co and C60/Py bilayer samples and observed via ferromagnetic resonance and point contact Andreev reflection. The molecular properties of C60 can be manipulated by an adjacent ferromagnetic material at ferromagnetic resonance dissipating energy into the C60. This changes the frequency/energy of molecular vibrations, as well as an enhanced photoemission from the C60. The changes can be correlated to spin pumping and phonon injection. The conductivity through a C60 layer is also increased during ferromagnetic resonance of the adjacent Py by up to 8% owing to increased phonon-assisted hopping steps.
Supervisor: Cespedes, Oscar ; Hickey, Bryan J. Sponsor: EPSRC
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available