We report a clock/logic/input structure for nanomagnet logic (NML) that implements a two-input slant-based OR gate with both clocking and input programming through current pulses. The clock line is a copper conductor embedded in a Si substrate with CoFe as a flux concentrator. Inputs are implemented with overlaid and dedicated bias lines. The programmability of such inputs allows us to test the same NML device for all possible input combinations. Results are determined by magnetic force microscopy. This scheme is easy to fabricate and can control thicker (20-30 nm) input nanomagnets. Close proximity of bias lines in such a structure allows us to investigate the effect of overlapping bias fields. We also report micromagnetic simulations that relate the slant in the output magnet to the dimensions of the input nanomagnets required to effect proper logic operation.Index Terms-Nanomagnet logic (NML), on-chip integration, programmable input.

The effect of nanomagnet spacing on required clock field has been studied by micromagnetic simulation for supermalloy (Ni79Fe16Mo5) dots with dimensions 90 × 60 × 20 nm3 and 120 × 60 × 20 nm3. Reduction of the inter-magnet spacing for both dimensions has resulted in reduction of the required clock field in the simulation. A dual e-beam exposure technique has been developed to allow fabrication of ultra dense features using conventional poly(methylmethacrylate) e-beam resist. Nanomagnet logic (NML) datalines of supermalloy dots with ∼10 nm and ∼15 nm spacing have been fabricated using dual e-beam exposure with a 3σ overlay accuracy of ∼4 nm. Fabricated NML datalines have been characterized using magnetic force microscopy for various clock fields. Datalines of both spacing have shown proper NML functionality with a clock field as low as 60 mT.

In this paper we study pipelined nanomagnet logic by simulating and comparing varying adjacent clock line structures. Unlike previous simulations, a realistic clock line shape is used in simulations to obtain a more accurate idea of whether or not these clock lines function properly. First, we simulate individual clock lines using Ansys Maxwell 2D according to the parameters of the fabricated clock lines. Then, these clock lines are placed adjacent to one another to simulate how data can propagate from one clock zone to another. Adjusting the clock line layer structure minimizes a dip in the magnetic field at the clock zone boundaries from 35% minimum below the clocking field to a 16% dip. These magnetic field profiles are then used in the object-oriented micromagnetic framework (OOMMF) to simulate lines of nanomagnets. By reducing the gap between contiguous clock lines, we show error free data propagation in the form of a ferromagnetically coupled line of nanomagnets.

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