Realization of Zero-Field Skyrmions in a Magnetic Tunnel Junction

Magnetic skyrmions are topologically protected noncollinear spin textures, which are regarded as promising information carriers for next-generation spintronic devices due to their small size and the low current density needed to drive their motion. Stability of skyrmions in zero external magnetic field is important for promoting fundamental studies and device applications. A few zero-field skyrmion-hosting materials have been developed, but none of them have been successfully integrated into a magnetic tunnel junction (MTJ), a crucial device for converting skyrmion information into an electrical signal. Here, a zero-field exchange-biased skyrmion material is developed and incorporated into an MTJ device. An Ir layer is inserted between the antiferromagnetic and ferromagnetic layers, which plays a crucial role in prohibiting interlayer diffusion under thermal annealing, resulting in simultaneous enhancement of exchange bias and thermal stability. The smallest zero-field skyrmions have a size of 100 nm at room temperature. The zero-field skyrmion material is then integrated into a perpendicularly magnetized MTJ, leading to the first demonstration of zero-field skyrmions in an MTJ, which is an important step toward developing skyrmion-based spintronic devices.