UCSD Engineers Use Focused Light to Rewrite Magnetic Memory at High Speed

Engineers at the University of California San Diego (UCSD) have demonstrated a method to rewrite magnetic memory using specially engineered light pulses, potentially overcoming the energy and speed limitations of traditional magnetic field-based storage. By focusing an ultrafast laser beam into a region smaller than 1.36 micrometers, the research team achieved helicity-independent magnetization reversal in magnetic stacks significantly thicker than previously possible.

Advancing Optical Switching Capabilities

Traditional magnetic data storage relies on external magnetic fields to flip bits between binary states, a process that consumes significant energy and restricts switching speeds. While optical switching has been explored as an alternative, it was previously limited to thin magnetic stacks of no more than three layers. Thicker materials typically suppressed the switching effect, and earlier methods often required specific light polarization, complicating practical implementation.

To bypass these constraints, the UCSD team focused on modifying the light itself rather than the magnetic material. By using an ultrafast laser with an engineered beam shape and size, researchers successfully induced magnetization reversal in a nine-layer stack of platinum and cobalt. This approach allows for the manipulation of local heating and optical torques, enabling the material to respond to light in ways previously thought impossible.

Mechanism and Future Potential

The switching process utilizes a sequence of ultrafast laser pulses. Initial pulses concentrate energy to heat a tiny spot, creating a reversed magnetic area, while subsequent pulses expand this region to a stable state. According to the research team, this optical method could eventually operate more than 1,000 times faster than conventional magnetic field switching. Furthermore, because the density of the memory is determined by the focus of the light beam, shrinking the beam size could allow for significantly higher data storage density.

While the results represent a major shift in controlling magnetism, the technology remains in the experimental stage. The specialized ultrafast lasers currently required are not yet integrated into standard electronic systems. The team is now exploring ways to use lasers more compatible with existing hardware and aims to further confine light using optical structures to reach sub-hundred-nanometer scales. The findings were recently published in the journal Nature Communications.