Chip-Sized Plasma Switch Fires Picosecond Pulses to Flip Magnetic Memory

For decades, one of the most stubborn bottlenecks in building faster, greener computer memory has been a simple question of timing: how do you deliver an electrical pulse short enough and powerful enough to flip a magnetic bit in a few trillionths of a second, without dragging a room-sized laser into the picture? A team at the National University of Singapore now believes it has cracked the problem. In a study published in Nature Electronics, researchers led by Xinhou Chen and Hyunsoo Yang describe an all-electric, on-chip pulse generator built around a nanoscale plasma discharge that produces picosecond electrical bursts with amplitudes exceeding 100 volts and a slew rate of 21 volts per picosecond. Using these pulses, the team demonstrated field-free switching of magnetization in cobalt/platinum/cobalt magnetic trilayers, achieving writing energies four orders of magnitude lower than those required with conventional long pulses.

The significance of the result lies in what it removes from the equation. Spin–orbit torque (SOT) switching, the physical mechanism at the heart of the work, allows engineers to reverse the direction of magnetization in a nanoscale magnetic layer by injecting an in-plane current into an adjacent heavy metal. The current’s spin angular momentum is transferred to the magnet, exerting a torque that can tip its north and south poles. Because the effect is purely electrical, it has long been viewed as the natural write mechanism for next-generation magnetic random-access memory (MRAM), a technology that stores data in magnetic orientations rather than electric charges and therefore retains information even when power is removed. The catch has always been speed and energy: writing reliably with conventional electronics has typically required pulses lasting microseconds or longer, dissipating far more energy than an ideal memory cell should.

Picosecond pulses, by contrast, promise a dramatic shortcut. When the write pulse is compressed from microseconds down to a few trillionths of a second, the energy delivered scales down accordingly, and the magnetization dynamics themselves enter a faster, more coherent regime. But generating such pulses has traditionally demanded mode-locked laser systems and photoconductive switches, an approach that is bulky, expensive, power-hungry and fundamentally incompatible with the dense, CMOS-integrated architecture a commercial memory chip requires. The Singapore team’s answer was to abandon optics altogether and exploit a phenomenon more familiar to high-voltage engineers than to memory designers: the abrupt, avalanche-like breakdown of a plasma confined within a nanoscale gap.

The device works by charging a capacitor-like structure and then letting a nanometer-scale gap break down in a controlled discharge. When the voltage across the tiny gap exceeds a threshold, a nanoplasma forms almost instantaneously, and the stored charge dumps through the gap in a burst measured in picoseconds. Because the discharge is triggered purely by voltage, the entire pulse generator can be patterned lithographically alongside the magnetic devices it is meant to drive, making it genuinely chip-compatible. In their experiments, the researchers showed that the generator could produce pulses as short as 6.4 picoseconds with peak amplitudes above 100 volts, figures that place the device firmly in the territory previously accessible only to optical pump–probe setups.

Armed with this electrical pulse source, the team turned to their magnetic test structures: trilayers of cobalt separated and sandwiched with platinum, a configuration in which the two cobalt layers are antiferromagnetically coupled through the platinum spacer. This symmetry is not incidental. Field-free switching, meaning deterministic reversal of perpendicular magnetization without the aid of an external magnetic field, has been a long-standing goal in the SOT community, because an external field would be impractical to supply in a dense memory array. Earlier work from the same group and others had shown that synthetic antiferromagnetic trilayers can achieve field-free switching at sub-nanosecond timescales; the new study pushes that capability into the picosecond domain using a fully integrated electrical source.

The headline result is a sweeping energy comparison. When the researchers varied the pulse width from 100 microseconds all the way down to 6.4 picoseconds, they found that the energy required to switch the magnetization fell by four orders of magnitude. In other words, writing the same magnetic bit with a picosecond pulse costs roughly ten thousand times less energy than writing it with the microsecond pulses that have been standard in laboratory demonstrations. For an industry in which data-center memory power consumption is a growing fraction of global electricity use, a four-decade reduction in per-bit write energy is the kind of number that translates directly into real-world impact.

Perhaps the most intriguing part of the study is the physical explanation the authors offer for why the picosecond regime is so efficient. Naively, one might expect that a shorter pulse delivers less total torque and therefore makes switching harder, not easier. The team found instead that ultrafast Joule heating plays a constructive role: the intense, brief current pulse transiently heats the magnetic layer, lowering the energy barrier that the magnetization must overcome to reverse. This thermally assisted switching mechanism, the authors argue, contributes significantly to the enhanced efficiency observed in the picosecond regime. The idea echoes concepts from heat-assisted magnetic recording, where a laser briefly softens a recording medium before writing, but here the heating is delivered electrically, on the same timescale as the write operation itself, and confined to the immediate vicinity of the bit.

The researchers verified the switching behavior using magneto-optical Kerr effect (MOKE) microscopy, which images the out-of-plane magnetization of the devices before and after pulse application, confirming deterministic reversal under the 6.4-picosecond pulses. They also extended their analysis to ferrimagnetic films, examining how the critical current density and switching energy depend on pulse width across both ferro- and ferrimagnetic systems, a comparison that matters because compensated ferrimagnets are among the most promising materials for ultrafast, thermally robust spintronic memory.

The broader implications reach beyond a single memory technology. An on-chip source of picosecond, high-voltage electrical pulses is a tool, not just a component: the same generator that writes magnetic bits could, in principle, drive ultrafast electronics experiments, terahertz-scale signal generation, or other spintronic operations that have historically been gated by access to laser facilities. Because the nanoplasma switch builds on prior demonstrations of nanoplasma-enabled picosecond switching for ultrafast electronics, the work also signals a convergence between two previously separate research communities, high-speed electrical engineering and magnetism, that now share a common enabling device.

Challenges remain before such pulse generators appear inside commercial MRAM products. The discharge-based approach must prove its endurance over billions of write cycles, its uniformity across millions of cells on a wafer, and its compatibility with the back-end-of-line thermal budgets of CMOS manufacturing. The peak voltages involved, while modest in absolute terms, will need careful management in dense circuit environments. Still, the demonstration marks a conceptual milestone: picosecond spin–orbit torque switching, once the exclusive province of optics laboratories, can now be triggered by nothing more exotic than a voltage applied to a patterned on-chip structure. If the endurance and scalability questions can be answered, the all-electric nanoplasma pulse generator may well become the write engine of a new generation of memory, one that flips its bits in trillionths of a second while sipping, rather than gulping, energy.

Subject of Research: An all-electric on-chip nanoplasma pulse generator enabling picosecond field-free spin–orbit torque switching in magnetic heterostructures

Article Title: An all-electric on-chip nanoplasma pulse generator for picosecond field-free spin–orbit torque switching in magnetic heterostructures

Article References: Chen, X., Zhao, S., Pu, Y., Yang, Q., & Yang, H. (2026). An all-electric on-chip nanoplasma pulse generator for picosecond field-free spin–orbit torque switching in magnetic heterostructures. Nature Electronics. https://doi.org/10.1038/s41928-026-01699-w

Image Credits: AI Generated

DOI: 10.1038/s41928-026-01699-w

Keywords: spin–orbit torque, nanoplasma, picosecond pulses, MRAM, magnetization switching, magnetic heterostructures, field-free switching, Joule heating, spintronics, Nature Electronics, energy-efficient memory, cobalt platinum trilayers