Thermal ‘tug-of-war’ enables memory with 66× lower energy consumption

Researchers have developed a memory technology that can store and retain data using almost no electricity by controlling spin states through temperature changes.

The work, led by researchers from POSTECH and Chungnam National University, demonstrates non-volatile switching driven by temperature changes rather than electric currents. The approach could reduce energy consumption by up to 66 times compared with existing methods, and by as much as 452 times under ideal conditions. The study was published as an Inside Front Cover paper in Advanced Functional Materials.

As artificial intelligence (AI) drives demand for faster and more efficient data processing, energy consumption has become a major constraint. Large data centres already consume electricity on the scale of small cities, increasing the need for low-power memory technologies.

One promising candidate is spintronics, which encodes information using the spin of electrons rather than their charge. In such systems, the direction of electron spin represents binary states (0 and 1). Devices based on magnetic insulators are especially attractive because they avoid energy loss casued by current-induced heating.

Most existing approaches rely on strong electric currents to switch spin directions, resulting in high energy consumption. Temperature-based methods have been proposed as a lower-power alternative, but the spin orientation typically returns to its original state when the temperature returns to its original value, making non-volatile operation difficult.

The researchers overcame this limitation using thermal hysteresis—a phenomenon in which a system does not immediately return to its original state after being heated and cooled, but instead remains stable over a certain temperature range.

They built a bilayer structure by stacking two rare-earth iron garnets—gadolinium iron garnet (GdIG) and holmium iron garnet (HoIG). Both materials respond magnetically, but their spin directions change differently with temperature, so that over a specific temperature range they favour different orientations. Strong coupling between the layers, together with the intrinsic magnetic anisotropy of each material, gives rise to bistability—two distinct magnetic orientation states that remain stable within a certain temperature window.

The effect can be likened to a tug-of-war game. The two materials act as opposing teams, while temperature strengthens or weakens each side. When one side gains the upper hand, the system shifts in that direction. Like a rope held in place by friction, it does not easily flip back even if the support fades. This persistence is key to non-volatile behaviour, allowing the memory state to remain stable even as external conditions change.

The team successfully switched spin directions using only a small temperature change of about ±25 K and a modest magnetic field. Compared with conventional spin–orbit torque (SOT) methods, this approach reduces energy consumption by up to 66 times, and by as much as 452 times under ideal conditions.

Professor Hyungyu Jin said, “This study demonstrated that spin states can be controlled and maintained using only temperature changes. It could be an important step toward ultra-low-power memory devices for the AI era.”

This work was supported by the Samsung Research Funding & Incubation Center of Samsung Electronics and by grants from the National Research Foundation of Korea (NRF) funded by the Korea government (MSIT).