Permanent Electride Magnets Induced by Quasi-Atomic Non-Nucleus-Bound Electrons.

Hwang, Jeong Yun; Lee, Seung Yong; Lee, Kimoon; Regmi, Binod; Lee, Nahyun; Lim, Dong Cheol; Koo, Heejeong; Lee, Wooyoung et al. · Adv Mater · 2025

basic_science · Level V

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Abstract

Interstitial quasi-atomic electrons (IQEs) in the quantized energy levels of positively charged cavities possess a substantial own magnetic moment and control the magnetism of crystalline electrides depending on the interaction with surrounding cations. However, weak spin-orbit coupling and gentle exchange interaction restricted by the IQEs preclude a large magnetic anisotropic, remaining a challenge for a hard magnetism. It is reported that 2D [Re<sub>2</sub>C]<sup>2+</sup>·2e<sup>-</sup> electrides (Re = Er, Ho, Dy, and Tb) show the permanent magnetism in a ferrimagnetic ground state, mimicking the ferrites composed of magnetic sublattices with different spin polarizations. Magnetic interaction between Re-spin lattice and IQE-spin lattice in the [Re<sub>2</sub>C]<sup>2+</sup>·2e<sup>-</sup> electrides results in a large magnetocrystalline anisotropy and high coercivity, giving a maximum energy product of 15 MGOe. It is demonstrated that the spontaneous breaking of magnetic IQE-sublattice through substitution with paramagnetic elements produces a crossover into an antiferromagnetic spin ordering of Re-sublattice, implying that the magnetic sublattice of IQEs drives the permanent magnetism.