Electrides: From fundamental concepts to tunable magnetism in layered systems

Abstract

Layered electrides, characterized by anionic electrons confined in interstitial sites, present a unique platform for engineering exotic electronic and magnetic phenomena. This study employs a combination of density functional theory, maximally localized Wannier functions, and dynamical mean-field theory to systematically investigate the emergence and control of magnetism in a family of twelve isostructural $M_{2}X$ electrides (M $=$ Ca, Sr, Ba; X $=$ N, P, As, Sb). We demonstrate that the magnetic state is governed by the local geometry of the interstitial cavities, specifically by the ratio of intra- to inter-layer metal–metal distances ($l_{\text{intra}}/l_{\text{inter}}$). A magnetic ground state emerges when this ratio falls below unity, a condition that can be selectively induced by hydrostatic pressure. Electronic structure analysis reveals that this transition is driven by a Stoner-like instability, associated with the flattening of an electride-derived band at the Fermi level. Our DMFT calculations confirm the presence of significant electron correlations and spin fluctuations near the magnetic instability, indicative of a correlated metallic state. The strong coupling between magnetic ordering and the crystal lattice, evidenced by concurrent structural and magnetic phase transitions, underscores a robust magneto-structural coupling. We establish simple empirical criteria based on atomic radii and electronegativities to predict magnetic behavior within this family of compounds. These findings provide a comprehensive microscopic understanding of magnetism in layered electrides and establish design principles for creating and tuning magnetic materials via pressure or chemical substitution from non-magnetic elements.