Fabrication and performance enhancement of TMR-Superconducting composite magnetic sensors for weak magnetic field detection

The tunneling magnetoresistance (TMR) effect, utilizing the CoFeB/MgO/CoFeB magnetic tunnel junction (MTJ) structure, has seen a surge in research interest owing to its pronounced sensitivity to magnetic fields. However, advancements in TMR technology have plateaued in recent times. In response, this study explores the integration of TMR with superconductivity to form a TMR-superconducting composite magnetic sensor, aiming to amplify the external magnetic field effect and improve sensor performance. Such sensors offer significant promise for applications in detecting feeble magnetic fields due to their compact dimensions, minimal energy consumption, and exceptional magnetic field resolution. Despite their potential, manufacturing challenges persist. This paper focuses on the meticulous fabrication of the TMR's critical thin film layer and its subsequent patterning. Moreover, we propose an innovative technique utilizing magnetron sputtering to deposit a niobium (Nb) layer atop the TMR structure, followed by intricate patterning to successfully construct a TMR-superconducting composite film. This novel approach importantly diminishes the interspace between TMR and superconducting layers compared to traditional bonding methods, thereby enhancing device performance. Experimental assessments of the device constructed superconducting loops, contrasted with traditional bonding process, demonstrate that sputtering -based sensor exhibit better magnetic field resolution. Consequently, TMRsuperconducting composite sensors realized via the sputtering technique hold distinct advantages in weak magnetic field detection.