In a groundbreaking study published in the journal *Materials Research Express* (which translates to *Expressions of Materials Research*), a team of scientists led by Bijay Khanal from Texas State University has unveiled new insights into the magnetic properties of multilayered materials, with significant implications for the energy sector. The research focuses on the interplay between magnetism and superconductivity, opening doors to potential advancements in energy-efficient technologies.
The study investigates the behavior of [Pt/Co/Cu] multilayers, where the thickness of the cobalt (Co) layer is systematically varied. “By tuning the Co thickness, we observed a fascinating transition in the magnetic properties of these multilayers,” explains Khanal. As the Co thickness increases from 0.6 to 1.2 nanometers, the magnetic hysteresis loops transform from nearly square to a distinctive “wasp-waisted” shape. This change is accompanied by a progression in the magnetic domain structure, evolving from sparse to dense worm-like domains, as revealed by room-temperature magnetic force microscopy (MFM).
One of the most intriguing findings is the observation of an antisymmetric excess Hall signal in the stack with a Co thickness of 1.2 nm. This signal, obtained after subtracting the ordinary and anomalous Hall components, hints at the presence of novel magnetic textures or topological effects. “This antisymmetric signal is a clear indication of something unusual happening at the nanoscale,” Khanal notes.
The researchers also explored the integration of superconducting niobium (Nb) layers with the magnetic multilayers. They found that adding Nb layers beneath the magnetic multilayer preserves the wasp-waisted hysteresis loops and MFM contrast, but a thicker Nb layer of 120 nm modifies the hysteresis loop. Interestingly, placing a 60 nm Nb layer above the magnetic multilayer reduces the MFM contrast. These observations provide crucial design rules for combining conventional superconductivity with magnetic multilayers.
Perhaps the most exciting discovery is the observation of a progression from worm-like to isolated skyrmion-like domains under the application of a perpendicular magnetic field at low temperatures. Skyrmions, which are tiny, swirling magnetic textures, have garnered significant attention for their potential use in ultra-dense data storage and energy-efficient computing.
The study also reveals that Nb–[Pt/Co/Cu] heterostructures exhibit the expected suppression of the critical temperature (T_c) with decreasing Nb thickness, with an additional reduction relative to single-layer Nb films. This finding underscores the complex interplay between magnetism and superconductivity in these heterostructures.
The implications of this research are far-reaching, particularly for the energy sector. The ability to manipulate magnetic properties at the nanoscale could lead to the development of more efficient energy storage devices, advanced magnetic sensors, and novel computing technologies. “Our findings provide a roadmap for integrating magnetism and superconductivity, which could pave the way for next-generation energy technologies,” Khanal says.
As the world grapples with the challenges of climate change and the need for sustainable energy solutions, research like this offers a glimmer of hope. By unraveling the intricate dance between magnetism and superconductivity, scientists are not only expanding our fundamental understanding of these phenomena but also laying the groundwork for innovative technologies that could transform the energy landscape.