A Predictive 4D Electrostatic Framework for Rare-Earth-Free Permanent Magnet Screening Curie Temperature, Magnetic Hardness, and Coercivity from a Classical Phase-Locking Model

Rare-earth permanent magnets underpin every electric motor, wind turbine, and MRI scanner built today, yet their supply chains are geographically concentrated and strategically fragile. Substituting them requires quantitative guidance on which candidate materials are worth synthesising-before expensive fabrication attempts are made. We present a three-stage predictive framework, grounded in the 4D Electrostatic Model, that calculates from crystal structure alone: (i) the Curie temperature T C , (ii) the dimensionless magnetic hardness parameter κ, and (iii) the ideal coercive field and domain-wall energy-the three quantities that together determine whether a magnet is useful. The central quantity is a magnetic phaselocking potential V mag (r) = λ mag k e / r 2 + δ 2 mag , calibrated against helium ionisation energetics and verified against eight well-characterised 3d ferromagnets. Predicted Curie temperatures fall within 10-17% of experiment for Fe 16 N 2 , τ-MnAl, MnBi, and FeCo; the hardness classification (soft, semi-hard, hard) is correct for every material tested. We further apply the framework to a novel class of graphene-intercalated iron films, predicting that N-doped graphene spacers can raise the magnetic anisotropy of FeCo thin films into the semi-hard regime (κ ≈ 0.5) while retaining M s > 1.3 MA/ma combination absent in any known rare-earth-free bulk material. All predictions are made by a MIT license open-source Python library, included as an appendix.