This paper demonstrates the design of nanomagnetic logic (NML) gates with multiple weighted inputs, which are magnetic equivalents of threshold logic gates (TLGs). We use micromagnetic simulations to show that NML TLGs can be constructed with minimum overhead compared to standard NML gates, and they significantly reduce device footprint and interconnection complexity of magnetic logic circuits. As an example, we design a full adder circuit using said TLGs and compare its performance to majority-gate-based NML.

We present the design and simulation of systolic information processing hardware that is comprised of single domain, Co/Pt magnets (i.e., out-of-plane nanomagnet logic or oNML). The designed circuit can identify instances of a preprogrammed bit sequence in streaming data. The systolic architecture 1) exploits unique benefits of the oNML device architecture such as nonvolatility and inherently pipelined logic with no memory overhead for holding the bits in the pipeline and 2) mitigates less desirable features of oNML such as nearest neighbor dataflow and longer device switching times when compared to a CMOS transistor. The designed layout is verified and analyzed by micromagnetic simulations. We quantify how the performance and energy of oNML information processing hardware compares to CMOS equivalents and conclude that the initial oNML design (including the overhead of magnetic field generation) is about an order of magnitude more power efficient at essentially iso-performance.

Nanomagnet logic (NML) emerges as a new field of spintronics. For NML operation, strong external magnetic clocking field pulses are required. The power-efficient generation of such fields is a challenge for magnetic computing. The idea of clocking Co/Pt nanomagnets with stray field from the domain wall of a Permalloy stripe was proposed in the earlier study. Here, we present a micromagnetic investigation of Co/Pt multilayer films that strongly interact with the stray field of a Permalloy domain wall conductor. The simulated domain patterns agree well with experimental results.

The switching behavior and the magnetization states of non-interacting Supermalloy (Ni79Fe16Mo5) nanomagnet arrays were studied by magnetic measurements and micromagnetic simulations. The switching-field distribution of the easy-axis hysteresis loop of the nanomagnets was broadened due to lithographic shape variations and thermal fluctuations. When cooled to a low temperature (100 K), the switching-field distribution of the loop was reduced and its squareness ratio became higher. We found strong remanent magnetization along the hard axes of the nanomagnets, indicating the presence of metastable states and end-domain states. An oscillating field with amplitude of 30 Oe was sufficient to destabilize these metastable states; however, a high oscillating field (amplitude > 250 Oe) is required to reduce the remanence to zero.

A majority gate for nanomagnetic logic with perpendicular magnetic anisotropy is presented. A novel technique of local focused ion beam irradiation generating artificial domain wall nucleation centers is used to enable directed signal flow and logic computation in an array of field-coupled nanomagnets. The switching behavior of the majority gate is characterized and logic operation is experimentally proven using magneto-optical and magnetic force microscopy. The findings are supported by numerical and micromagnetic simulations. Tolerance margins for fabrication and computing frequencies for correct operation are explored. The presented majority gate allows for complex, non-volatile logic with synchronous global clocking at room-temperature.

This paper presents a computational study of logic devices built from single-domain Co/Pt nanomagnets, where magnetic properties of the dots are engineered by an inhomogenous focused ion beam (FIB) irradiation. We develop a micromagnetic model for such Co/Pt dots and show that their reversal behavior and coupling to neighboring dots can be precisely engineered by the dose and spatial distribution of the irradiation. We demonstrate that magnetic logic circuits and nonvolatile memory devices with attractive performance figures can be built from asymmetrically irradiated dots.

We study the interaction between propagating domain walls in permalloy nanowires and nanomagnetic dots made of Co/Pt multilayers. The magnetic behavior of dots placed above/below the domain wall conductor is strongly influenced by the field of the wall. Using micromagnetic simulations we show that the field generated by the domain wall can switch the coupled dots to their magnetically ordered ground state. This effect can be exploited for clocking magnetic field-coupled devices and possibly substitute electrical clocking structures.

Nanomagnet Logic (NML) emerges as a promising candidate of novel “beyond CMOS” technology. The main goal of this dissertation is to implement computational study on Co/Pt-based NML devices. We developed a model to describe the switching behavior and predicted non-reciprocal coupling from partially irradiated Co/Pt magnets. We demonstrated that with non-reciprocal coupling, the information flow can be well-controlled and error-free ordering can be achieved in large-scale NML circuits.

Nanomagnet Logic (NML) is widely considered to be one of the promising for “beyond-CMOS” nanoscale architectures. So far only relatively simple circuits (nanomagnetic logic gates and adders) have been studied experimentally and in simulations. Here we investigate the possibility of building larger-scale computing devices from out-of-plane NML. We designed a systolic pattern matcher circuit that is in principle scalable to arbitrary number of nanomagnets and can match arbitrarily long patterns in an incoming data stream. The design of this systolic architecture for NML makes an important step toward large-scale devices.

An experimental and computational study of coupling between lithographically fabricated, near-single-domain nanomagnets is presented. Pairs of coupled nanomagnets were fabricated, and their switching properties were characterized by a vibrating sample magnetometer with vector coils. Coupling fields between on-chip nanomagnets compete with (known) magnetic fields that are externally generated. Consequently, nanomagnets flip in the direction of the stronger contribution. Using this method, the volume-averaged coupling field can be directly measured. The experimental data was compared to results from micromagnetic simulations and macrospin models. Correlating the experimental results with simulations reveals the details of the switching process of nanomagnets, and shows the limitations of the macrospin model.

Nanomagnet Logic (NML) emerges as one of the promising “beyond CMOS” computing architectures. Proposed NML devices require magnetic field clocking, generated by a power-hungry clocking structure. We recently proposed clocking nanomagnets with magnetic domain walls. This paper presents a combined experimental and computational study, exploring the interaction between Co/Pt nanomagnets and Permalloy domain walls. Our micromagnetic simulations verified the feasibility of achieving error-free antiferromagnetic ordering with the introduced clocking scheme.

A compact model for the design of nanomagnetic logic based on experiments with field-coupled nanomagnets is presented. Two different types of dots for signal propagation in a wire and logic operations in a majority gate are introduced. The switching behavior and the interaction of fabricated nanomagnets is analyzed by MOKE measurements. Partial irradiation with a focused ion beam (FIB) is used to influence the switching and the interaction of the utilized nanomagnets. Experimental results are used to calibrate the nanomagnetic compact models. Investigations on nanomagnetic wires and an XOR gate are performed. Simulations show that the error rate mainly depends on the switching field variations from dot to dot and the strength of the coupling field between the dots. High coupling fields by small gaps between the nanomagnets and accurate control of switching field variations by partial FIB irradiation turn out to be the key for realizing reliable NML systems.

In this paper we investigate error rates of nanomagnetic logic devices with perpendicular magnetization by compact modeling. Two different types of nanomagnets for information propagation and logic computing are introduced. The switching behavior of field-coupled nanomagnets is measured and analyzed. A compact model is derived from physics and experimental results are applied to the magnetic compact model. General requirements for fabrication parameters and clocking fields for reliable operation are extracted. We perform simulations and measurements on single devices to demonstrate the accuracy of the macro-model. Simulations on complex systems show that the error rate of a field-coupled magnetic system strongly depends on the variation of the switching field and the strength of the coupling field between the nanomagnets. The error rate of a 1-bit full adder is investigated for varying dot parameters. The results demonstrate the importance of fast simulation tools for investigations on the design of nanomagnetic computing devices and systems.

Nanomagnetic Logic (NML) is a novel nanoscale computing paradigm based on field-coupled single-domain nanomagnets. Most of the studies so far have been focused on permalloy, where the easy axis of magnetization is in-plane. Co/Pt multilayer films, which exhibit large perpendicular anisotropy, were recently proposed as promising media for implementing NML. The operation of NML devices is based on magnetic ordering. Frustrations of ordering will result in computing errors. In this paper, we explore the sources of errors in Co/Pt multilayer based NML observed in our experimental and simulation studies. We analyze the mechanisms of error formation based on simulations and provide strategies to avoid these errors.

In Nanomagnetic Logic (NML), computing operations are performed by non-volatile, field-coupled nanomagnets. For information propagation in nanomagnetic wires between logic gates, directed signal flow has to be implemented in the field-coupled devices. In this paper we present the solution for directed information propagation in a wire realized in NML with perpendicular magnetization. For the first time, non-reciprocal signal flow is experimentally demonstrated for field-coupled nanomagnets and homogeneous clocking fields. Micromagnetic simulations are performed and field-coupled nanomagnets are fabricated by focused ion beam (FIB) lithography and ion beam etching. Partial irradiation with a FIB is investigated to tailor the switching behavior of the nanomagnets. Three coupled nano-magnets in a wire are measured to verify the simulation results. Non-reciprocal field-coupling of the nanomagnets is proven by experiments within a nanomagnetic wire.

This paper proposes the use of Cellular Non-Linear Networks (CNNs) as physical uncloneable functions (PUFs). We argue that analog circuits offer higher security than existing digital PUFs and that the CNN paradigm allows us to build large, unclonable, and scalable analog PUFs, which still show a stable and repeatable input-output behavior. CNNs are dynamical arrays of locally-interconnected cells, with a cell dynamics that depends upon the interconnection strengths to their neighbors. They can be designed to evolve in time according to partial differential equations. If this If this equation describes a physical phenomenon, then the CNN can simulate a complex physical system on-chip. This can be exploited to create electrical PUFs with high relevant structural information content. To illustrate our paradigm at work, we design a circuit that directly emulates nonlinear wave propagation phenomena in a random media. It effectively translates the complexity of optical PUFs into electrical circuits.

Focused ion beam irradiation on ferromagnetic Co/Pt films permits controlled modification of the coercivity. This is demonstrated experimentally and mapped to micro-magnetic simulations. Temperature measurements prove the thermal stability of films and nanodots in an application relevant temperature range. For the first time, Extraordinary Hall-Effect measurements are performed at a single-domain ferromagnetic nanodot with a target size of 250 nm in a Hall current device. This verifies the thermal stability and the read-out ability of the magnetic bistable states. Thus, the ultra-low volume magnetic Co/Pt dots fulfill the demands for use in field-coupled logic devices.

Co/Pt multilayers were proposed as a new promising media for Nanomagnet Logic computing. Modeling of irradiated Co/Pt films is challenging as Focused Ion Beam (FIB) irradiation locally changes the magnetic properties of the Co/Pt film. We implemented a computational model of partially irradiated nanodots and explained how to exploit asymmetric coupling for designing nanowires and logic gates.

This paper proposes the use of Cellular Non-Linear Networks (CNNs) as physical uncloneable functions (PUFs). We argue that analog circuits o®er higher security than existing digital PUFs and that the CNN paradigm allows us to build large, unclonable, and scalable analog PUFs, which still show a stable and repeatable input output behavior. CNNs are dynamical arrays of locally-interconected cells, with a cell dynamics that depends upon the interconnection strengths to their neighbors. They can be designed to evolve in time according to partial di®erential equations. If this equation describes a physical phenomenon, then the CNN can simulate a complex physical system on-chip. This can be exploited to create electrical PUFs with high relevant structural information content. To illustrate our paradigm at work, we design a circuit that directly emulates nonlinear wave propagation phenomena in a random media. It e®ectively translates the complexity of optical PUFs into electrical circuits.