Vortex-State Dynamics and Noise Scaling in Magnetic Tunnel Junctions for Low-Field Spintronic Applications

Magnetic tunnel junctions (MTJs) operating in the vortex state offer a unique platform for probing spin-dependent transport and magnetization dynamics in confined geometries. However, their low-field detectability is fundamentally limited by intrinsic 1/f noise arising from magnetic and electronic fluctuations. In this work, we systematically explore the dependence of noise on device geometry, materials composition, and array configuration. Using cross-correlation measurements, we isolate the intrinsic vortex-state noise spectrum from extrinsic contributions of the measurement circuitry, enabling quantitative analysis of scaling behavior. The resulting trends reveal the interplay between vortex dynamics and magnetic anisotropy in determining noise performance. Finally, we implement these design principles in a vortex-MTJ-based magnetic gradiometer, directly linking microscopic noise mechanisms to macroscopic sensing functionality. These results establish a physics-based framework for engineering scalable, low-noise spintronic devices relevant to magnetic, biomedical, and quantum sensing technologies.