Simultaneous Coercivity and Size Determination of Magnetic Nanoparticles

Abstract

Magnetic nanoparticles are increasingly employed in biomedical applications such as disease detection and tumor treatment. To ensure a safe and efficient operation of these applications, a noninvasive and accurate characterization of the particles is required. In this work, a magnetic characterization technique is presented in which the particles are excited by specific pulsed time-varying magnetic fields. This way, we can selectively excite nanoparticles of a given size so that the resulting measurement gives direct information on the size distribution without the need for any a priori assumptions or complex postprocessing procedures to decompose the measurement signal. This contrasts state-of-the-art magnetic characterization techniques. The possibility to selectively excite certain particle types opens up perspectives in “multicolor” particle imaging, where different particle types need to be imaged independently within one sample. Moreover, the presented methodology allows one to simultaneously determine the size-dependent coercivity of the particles. This is not only a valuable structure–property relation from a fundamental point of view, it is also practically relevant to optimize applications like magnetic particle hyperthermia. We numerically demonstrate that the novel characterization technique can accurately reconstruct several particle size distributions and is able to retrieve the coercivity–size relation of the particles. The developed technique advances current magnetic nanoparticle characterization possibilities and opens up exciting pathways for biomedical applications and particle imaging procedures.

Perspective: magnetic nanoparticles in theranostic applications

“…In this context, we recently improved the characterization performance of MRX by using a pulsed sinusoidally or circularly polarized AC field instead of a DC pulse 91 . Intriguingly, the response of the particles to such fields is very different depending on whether the field amplitude is larger or smaller than a, particle-dependent, critical value 92 .…”

Noise Power Properties of Magnetic Nanoparticles as Measured in Thermal Noise Magnetometry

“…The TNM simulations were performed with Vinamax [56]: an open-source macrospin simulation tool for magnetic nanoparticles, which was recently extended to simulate Brownian rotations of the particles [58]. The particles are considered spherical and uniformly magnetized.…”

Thermal Noise Magnetometry of magnetic nanoparticles: simulations and experiments

“…The thermal noise magnetometry simulations were performed with Vinamax [42]: a macrospin simulation tool for magnetic nanoparticles, which was recently extended with the ability to simulate Brownian rotations of the particles [43]. The shape of the sample holder was defined to closely resemble those used in the experiments and the magnetic field was evaluated in a rectangular detector with the same dimensions as the SQUID pickup coil.…”