We report magnetoelectric coupling in nanoparticle assemblies that persists to temperatures over 300 times lower than in previous studies. The ME response saturates at low temperature, revealing a quantum plateau of the coupling. A field dependence analysis shows a crossover from quadratic to linear behavior, captured by a phenomenological expansion C(B,T)≃C0(T)+a1(T)B+a2(T)B2. The magnitude of the extracted quadratic coefficient, ∣a2(T)∣, follows a power law ∣a2(T)∣∼T−α with α≈1.15, indicating proximity to a quantum critical regime. The observed saturation reflects a new intrinsic energy scale, distinct from finite-size or extrinsic effects. These results establish nanoparticle assemblies as a new platform for studying quantum magnetoelectric phenomena.
@article{arxiv.2509.24131,
title = {Quantum Saturation of Magnetoelectric Coupling in Fe$_3$O$_4$ Nanoparticles},
author = {Jian Huang and Fatemeh Aghabozorgi and Stephanie Brock},
journal= {arXiv preprint arXiv:2509.24131},
year = {2025}
}