[CCoE Notice] PhD Dissertation Defense

[Khator, Suresh]

PhD Dissertation Announcement


ELECTROCHEMICAL SYNTHESIS OF MAGNETIC MATERIALS FOR MAGNETIC RECORDING AND MEMS APPLICATIONS

Jinnie George

April23, 2012, ECE Conference Room, 10.30 A.M.

Committee: Dr. Stanko R. Brankovic (Chair), Dr. Paul Ruchoefft, Dr. Dmitri Litvinov, Dr. Alex Ignatiev, Dr. Lars Grabow


Thin films are widely used in the fabrication of MEMS devices and magnetic recording heads. As the critical dimensions of the devices scale down to nanometers, controlling the corrosion and stress in thin films play important role. The CoFe alloys and thin films having the highest magnetic flux density of 2.4T is the most popular choice for these applications. Sulfur containing additives like saccharin are added in CoFe electrodeposition bath to provide desirable properties. The effect of saccharin incorporation during electrodeposition process on the properties of CoFe films is studied in this research.

In-situ stress measurements were performed to determine the reduction in stress with increasing saccharin concentrations in the bath and an analytical model was developed to explain phenomenological dependence of the maximum stress level in CoFe films as a function of saccharin concentration in the bath. However, saccharin incorporation in CoFe bath lowers the corrosion resistance of CoFe films. In this study, experiments have been performed to understand the corrosion potential dependence on the sulfur incorporation mechanisms in CoFe films and the analytical model explaining this dependence was developed based on mixed potential theory.

In the quest to increase the areal density of hard drives, the bit size needs to be decreased. Hence, new magnetic sensors that provide high sensitivity and magnetoresistance ratio have to be developed. As a part of this research thesis, the novel magnetic field sensors were fabricated based on electrodeposited CoFe nanocontacts. The CoFe nanocontacts, ~70nm in diameter, embedded in insulating Al2O3 layer which separates two plane parallel ferromagnetic layers represent the basic magnetic field sensor design. The CoFe nanocontacts had varying concentrations of oxygen incorporated and demonstrated magnetoresistance ratio as high as 3000%. Low temperature measurements were also performed to understand the transport mechanisms in these magnetic nanocontacts.




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