Study of Magnetic Nanoparticle Spectrum for Magnetic Nanothermometry

This paper reports on a new system of magnetic nanoparticle spectrometer to measure the magnetization spectrum of a magnetic nanoparticle based sample induced in alternating magnetic field with low frequency ( f = 192 Hz) for noninvasive magnetic nanothermometry. The achieved magnetic nanothermometer employs the measured fundamental and third harmonics in ac magnetic field (fundamental and second harmonics in ac plus dc magnetic fields), as well as the Fourier series of the first-order Langevin function, to calculate temperature. Our experimental result shows that the maximum error of temperature probing is about 0.67 K with a standard deviation of 0.29 K in ac magnetic field whereas it is about 0.48 K with a standard deviation of 0.19 K in ac plus dc magnetic fields with response time of 1 s. Furthermore, experimental results indicate that an increase in response time from 1 to 8 s improves the accuracy of temperature probing from 0.29 to 0.08 K in ac magnetic field (from 0.19 to 0.06 K in ac plus dc magnetic fields). In addition, the dependence of temperature probing accuracy on measurement signal-to-noise ratio of magnetic nanoparticle magnetization spectrum is discussed by comparing the measured second and third harmonics, which are induced in ac + dc and ac magnetic fields, respectively.