Degree Granting Department
Boolean logic, Emerging devices, energy minimization, multilayer, nanofabrication
The continuous scaling down of the metal-oxide-semiconductor field-effect transistor (MOSFET)
has improved the performance of electronic appliances. Unfortunately, it has come to a
stage where further scaling of the MOSFET is no longer possible due to the physical and the
fabrication limitations. This has motivated researchers towards designing and fabricating novel
devices that can replace MOSFET technology. Carbon Nanotube Field-Effect Transistors, Single
Electron Tunneling Junctions, Nano-Magnetic Devices, and Spin Field-Effect Transistors are some
prospective candidates that could replace MOSFET devices. In this dissertation, we have studied
the computational performance of Nano−Magnetic Devices due to their attractive features such
as room temperature operation, high density, robustness towards thermal noise, radiation hardened
nature and low static power dissipation.
In this work, we have established that data can be propagated in a causal fashion from a driver
cell to the driven cells. We have fabricated a ferromagnetic wire architecture and used a magnetic
force microscopy (MFM) tip to provide localized magnetic inputs. This experiment validated two
important phenomena; (1) a clocking field is essential to propagate data and (2) upon removal of the
clocking field data can be propagated according to the input data.
Next, we have fabricated and captured MFM images of a nano-magnetic logic architecture
that has computed the majority of seven binary variables. The architecture was designed by interconnecting
three three-input majority logic gates with ferromagnetic and antiferromagnetic wire
architectures. This seven input majority logic architecture can potentially implement eight different
logic functions that could be configured in real-time. All eight functions could be configured by
three control parameters in real-time (by writing logic one or zero to them).
Even though we observed error-free operations in nano-magnetic logic architectures, it became
clear that we needed better control (write/read/clock) over individual single layer nano-magnetic
devices for successful long-term operation. To address the write/clock/read problems, we designed
and fabricated amultilayer nano-magnetic device. We fabricated and performed a set of experiments
with patterned multilayer stacks of Co/Cu/Ni80Fe20 with a bottom layer having a perpendicular
magnetization to realize neighbor interactions between adjacent top layers of devices. Based on the
MFM images, we conclude that dipolar coupling between the top layers of the neighboring devices
can be exploited to construct three-input majority logic gates, antiferromagnetic and ferromagnetic
Finally, we have experimentally demonstrated a magnetic system that could be used to solve
quadratic optimization problems that arise in computer vision applications. We have harnessed
the energy minimization nature of a magnetic system to directly solve a quadratic optimization
process. We have fabricated a magnetic system corresponding to a real world image and have
identified salient features with true positive rate more than 85%. These experimental results feature
the potentiality of this unconventional computing method to develop a magnetic processor which
solves such complex problems in few clock cycles.
Scholar Commons Citation
Karunaratne, Dinuka, "Nano-Magnetic Devices for Computation" (2013). Graduate Theses and Dissertations.