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| Main Authors: | , , , , |
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| Format: | Preprint |
| Published: |
2024
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2405.11641 |
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Table of Contents:
- In application as hyperthermia and nanowarming, power dissipation arises when the time-dependent magnetization $M(t)$ of an out-of-equilibrium system of nanoparticles lags behind the applied field $H(t)$. The key parameter governing this process is the relaxation time $τ$ of the system, which induces a phase shift $ϕ_n$ between $H(t)$ and every nth harmonic component of $M(t)$. In this work, we present an expression for $M(t)$ in terms of $τ$ and the equilibrium magnetization, valid for any magnetic system exhibiting odd equilibrium response. From this calculation, we obtain a method for determining the effective $τ$ of a MNPs sample directly from the experimental measurement of $M(t)$. Additionally, we demonstrate that the power dissipation (SAR: Specific Absorption Rate) of any magnetic sample under a sinusoidal field can be obtained from the first harmonic component of $M(t)$. As an illustrative application, we explore the variation of $τ$ for magnetic MNPs in aqueous suspension during the melting process of the matrix. In this case, the change in $τ$ can be understood as a result of the reorientation of the MNPs in the direction of the applied field as the matrix becomes liquid.