Abstract
A quantummechanical equation of motion simulation for electronic transport has been developed. A tightbinding basis is used, which has the advantages that complex electronic structures can be described and systems with arbitrary geometry can be considered. It is used to investigate fundamental issues for transport in complex and inhomogeneous nanoscale systems.
The technique is applied to a number of simple systems to verify the validity of the approach and to investigate its potential scope. The method is also applied to a number of important problems in the ﬁeld of spintronics. Currentperpendiculartotheplane giant magnetoresistance (CPP GMR) in thin ﬁlm magnetic multilayers is simulated, and nonlocal interfaces resistances associated with meanfreepath eﬀects are considered. Conduction electron spinrelaxation is also simulated by incorporating the spinorbit interaction into the method. Spinrelaxation times for the technologically important materials copper and cobalt are calculated, and its eﬀect on transport
is simulated.
A significant meanfreepath eﬀect is observed for a simple model of CPP GMR. The nonlocal part of the interface resistance is found to depend upon the ordering of layers in a multilayer, and upon the size of the meanfreepath. However the GMR is barely modiﬁed by these eﬀects, and an interpretation is given which explains recent theoretical and experimental results on similar systems. A GMR of 67% is calculated for a realistic device structure, Co4 Cu3 Co4 , and the eﬀect is found to be dominated by spindependent interface resistances.
The direct simulation of spinrelaxation by the incorporation of the spinorbit
interaction is the ﬁrst such calculation of its kind. Spin relaxation times of 25ps and 0.4ps, for Cu and Co respectively have been calculated  assuming realistic resistivities. These times are in good agreement with recent optical and transport measurements.
The technique is applied to a number of simple systems to verify the validity of the approach and to investigate its potential scope. The method is also applied to a number of important problems in the ﬁeld of spintronics. Currentperpendiculartotheplane giant magnetoresistance (CPP GMR) in thin ﬁlm magnetic multilayers is simulated, and nonlocal interfaces resistances associated with meanfreepath eﬀects are considered. Conduction electron spinrelaxation is also simulated by incorporating the spinorbit interaction into the method. Spinrelaxation times for the technologically important materials copper and cobalt are calculated, and its eﬀect on transport
is simulated.
A significant meanfreepath eﬀect is observed for a simple model of CPP GMR. The nonlocal part of the interface resistance is found to depend upon the ordering of layers in a multilayer, and upon the size of the meanfreepath. However the GMR is barely modiﬁed by these eﬀects, and an interpretation is given which explains recent theoretical and experimental results on similar systems. A GMR of 67% is calculated for a realistic device structure, Co4 Cu3 Co4 , and the eﬀect is found to be dominated by spindependent interface resistances.
The direct simulation of spinrelaxation by the incorporation of the spinorbit
interaction is the ﬁrst such calculation of its kind. Spin relaxation times of 25ps and 0.4ps, for Cu and Co respectively have been calculated  assuming realistic resistivities. These times are in good agreement with recent optical and transport measurements.
Original language  English 

Qualification  Doctor of Philosophy 
Awarding Institution 

Supervisors/Advisors 

Award date  23 Nov 2005 
Publisher  
Publication status  Published  2005 