For decades now, microelectronic circuits have been exclusively built from transistors. An alternative way is to use nano-scaled magnets for the realization of digital circuits. This technology, known as nanomagnetic logic (NML), may offer significant improvements in terms of power consumption and integration densities. Further advantages of NML are: non-volatility, radiation hardness, and operation at room temperature. Recent research focuses on the three-dimensional (3D) integration of nanomagnets. Here we show, for the first time, a 3D programmable magnetic logic gate. Its computing operation is based on physically field-interacting nanometer-scaled magnets arranged in a 3D manner. The magnets possess a bistable magnetization state representing the Boolean logic states '0' and '1.' Magneto-optical and magnetic force microscopy measurements prove the correct operation of the gate over many computing cycles. Furthermore, micromagnetic simulations confirm the correct functionality of the gate even for a size in the nanometer-domain. The presented device demonstrates the potential of NML for three-dimensional digital computing, enabling the highest integration densities.

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In this paper, we show that the time for domain wall (DW) nucleation in a magnet with perpendicular magnetic anisotropy (PMA) has to be considered to ensure reliable computation in perpendicular Nanomagnetic Logic (pNML). A theoretical model for the time-dependent DW nucleation probability in field-coupled nanomagnets is applied. Conditions for reliable computation in pNML circuits are derived depending on the nucleation time, the applied clocking field and the coupling strength between the nanomagnets. In the experiments, the DW nucleation time is measured in 400 nmwide magnetic nanowires using magneto-optical microscopy. The required field pulses in the 100 ns-range are generated by an on-chip coil. The field-dependent DW velocity in the magnetic nanowires is measured and the DW nucleation time is determined by experiment. The measurement results are compared to the theoretical model, which is calibrated by experimental data. Our results verify the presented model and pave the way for the further development of pNML circuitry.

Controlled domain wall motion and pinning in nanowires with perpendicular magnetic anisotropy are of great importance in modern magnetic memory and logic devices. Here, we investigate by experiment the DW pinning and depinning from a notch in a magnetic nanowire, under the influence of combined in- and out-of-plane magnetic fields. In our experiment, the perpendicular magnetization of the Co/Pt nanowires is tilted with the help of sub-μs in-plane field pulses generated by an on-chip coil. Consequently, the energy density of the DW is decreased and the depinning field of the notch is reduced. A theoretical model is applied and compared to the measurement results. The DW depinning mechanism and the DW type are further investigated by micromagnetic simulations.

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