High-resolution magnetic nanoparticle temperature measurement method based on dual-frequency magnetic field excitation

A new remote method for measuring temperature using magnetic nanoparticles (MNPs) is presented in this paper. The method involves exciting MNPs in a dual-frequency AC magnetic field, and using tunnel magnetoresistance to detect the mixing-frequency magnetization response signals. The effects of the excitation magnetic field amplitude and frequency on the temperature measurement were analyzed. Based on the relationship between the MNPs' magnetization harmonic amplitudes and their temperature, two-harmonic and four-harmonic temperature measurement models were established. The estimated temperature was obtained by the optimized parameter estimation algorithm. The temperature error was found to be less than 0.02 K using the two-harmonic model and less than 0.015 K using the four-harmonic model. (paper)