Effective measurement of magnetic tunneling junction noise based on the equivalent noise model

Abstract

The intrinsic noise of magnetic tunneling junctions (MTJs) limits the detectivity of tunneling magnetoresistance (TMR) sensors, as a key factor. Therefore, researches into the intrinsic MTJ noise are essential to enhance the TMR detectivity. However, the noise measurement result of the MTJ elements usually deviates from the intrinsic noise, especially when the MTJ resistance exceeds the range of impedance matching. This deviation results in the difficulty to enhance the TMR detectivity efficiently. In this paper, we propose an equivalent noise model to deal with the deviation between the output and the intrinsic noise. The model demonstrates the noise sources and the corresponding transfer functions in a normal noise measurement system. After calibrating the model parameters, we extract the thermal noise of some metal film resistors based on the model to indicate the model’s reliability. Furthermore, we apply the model to extract the intrinsic noise of MTJ elements with different resistances. The result indicates it is realizable to measure the intrinsic MTJ noise without considering the MTJ resistance range. Our work provides an effective way to obtain the intrinsic MTJ noise from the experimental output, which is important for the noise investigation on TMR sensors.