We describe the development of a magnetic logic device that is uniquely different from spintronic approaches based on magnetoresistive effects that derive from spin dependent transport of carriers. The core of our device is a thin film avalanche diode channel fabricated as a p-n bilayer. Because of the structural asymmetry, the carriers are sensitive to an in-plane magnetic field and the diode has a large magnetoresistance. We characterize our device as a current switch. The high- and low-current states are well defined and are determined by the magnetic field. Positive or negative field orientation with constant field strength is an appropriate selector. We then describe an integrated avalanche diode logic device in which the magnetic field is provided by the local fringe field from a patterned ferromagnetic film with nanometer dimensions. The magnetization orientation of the nanomagnet, and the sign of the magnetic field, is set by spin torque transfer (STT) using small amplitude current pulses. We describe how simple arrangements of these integrated devices can be used as dynamically reconfigurable logic gates. Reconfigurable Boolean AND/OR gates using early prototype structures with micron dimensions are shown. Scaling arguments that justify the plausibility of fabricating an integrated device with dimensions of 100 nm are presented. These arguments suggest that such a device could produce an output current driving STT write processes and provide fanout capability in an integrated network.
We describe a new mechanism for ultrafast active control of plasmon propagation. By using time-domain terahertz
spectroscopy, we demonstrate that electron spin state can influence plasmon propagation. Using a random spinplasmonic
medium consisting of a dense ensemble of bimetallic ferromagnetic (F)/nonmagnetic (N) microparticles, plasmon
propagation velocity, amplitude attenuation, phase retardation and magnetic field dependence are shown to be influenced
by electron spin accumulation in the nonmagnetic layers. The observation of electron spin accumulation is attributed to
the formation of a nonequilibrium spin-dependent potential barrier at the F/N interface that acts to resist the flow of a
spin-polarized plasmon current. This phenomenon is similar to the electrically-driven spin accumulation phenomenon
resulting from current transport between F/N layers. With this first demonstration of the merger between the plasmonics
and spintronics fields, we envision the realization of a new class of ultrafast spinplasmonic devices having unique
functionalities.
There have been several recent experiments involving spin injection and accumulation in mesoscopic metal samples,
using lateral spin valve structures. The results have been interesting from the perspectives of both fundamental physics
and applications. The resistance change associated with spin accumulation, ▵R, has been predicted to scale inversely
with sample volume and this inverse scaling has been observed over ten decades. A value of ▵R = 1 Ohm has been
reported, at room temperature, in a thin film Al wire structure with transverse dimensions of roughly 100 nm. High
values of ▵R have been observed in samples characterized by electrode interface resistances that vary by 6 decades.
Results are discussed within the framework of Johnson-Silsbee theory, and factors that limit inverse scaling are
identified. Lateral spin valves with dimensions of tens of nm may be competitive for device applications. Structures with
▵R of order 1 Ohm are superior to CPP spin valves of comparable dimensions. Prospects for improved performance, the
plausibility of a lateral spin valve with output levels of 10 Ohms and output impedance of 50 Ohms, and relevance to
hard drive read heads and integrated nonvolatile random access memory applications are discussed.
Conference Committee Involvement (4)
Quantum Sensing and Nanophotonic Devices IV
22 January 2007 | San Jose, California, United States
Quantum Sensing and Nanophotonic Devices III
23 January 2006 | San Jose, California, United States
Quantum Sensing and Nanophotonic Devices II
23 January 2005 | San Jose, California, United States
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