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Dynamic magnetic response of magnetic multicore particles: Competing anisotropies

Vladimir Zverev1, Ekaterina Novak1, Andrey A. Kuznetsov2, and Sofia Kantorovich2,*

  • *Contact author: sofia.kantorovich@univie.ac.at
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Phys. Rev. E 114, 045405 – Published 21 October, 2026

DOI: https://doi.org/10.1103/hb1v-81qm

Abstract

Magnetic multicore nanoparticles offer a versatile route to tuning magnetic response via particle geometry and internal structure. In this work, we investigate the dynamic magnetic behavior of ellipsoidal multicore particles, focusing on the interplay between elongation, intercore dipolar interactions, and magnetic anisotropy. Using Brownian dynamics simulations with explicit Néel and Brownian relaxation, combined with a spectral reconstruction method based on non-negative least-squares fitting of autocorrelation functions, we resolve the underlying relaxation modes across a wide frequency range. To interpret the simulation results, we develop a theoretical model for the static susceptibility of multicore ellipsoids that incorporates demagnetization effects within a modified mean-field framework. We show that while elongation merely shifts the Brownian relaxation peak in weakly interacting systems, it strongly enhances dipolar correlations at higher interaction strengths, leading to spectral broadening, multiple relaxation modes, and a redistribution of dissipation towards lower frequencies. As a consequence, elongated multicores display a specific loss power at low frequencies that is improved by over an order of magnitude, while maintaining their performance at high frequencies without any decrease. This behavior is particularly relevant for magnetic hyperthermia, where operational constraints limit the accessible frequency range. Our findings provide a microscopic basis for tailoring magnetic response through particle shape and internal architecture.

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Phys. Rev. E 114, 045405– Published 21 October, 2026
  • Received 19 May 2026
  • Accepted 24 August 2026
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