The ferromagnetic-semiconductor rare-earth nitrides have coupled magnetism/conductivity responses that promise facility to support superconducting spintronics, for which it is urgent to improve their electron mobility. We report exactly that advance, showing an order-of-magnitude enhanced mobility in GdN, the prototypical rare-earth nitride, enabling ballistic-transport barriers in magnetic Josephson junctions. To achieve the enhancement, the film was grown on the square net presented by the (001) surface of ${\mathrm{LaAlO}}_3$. The film's crystal structure was characterized by in situ reflection high-energy electron diffraction and ex situ x-ray diffraction and x-ray reflectivity to show the best crystallinity and smoothest surfaces we have accomplished to date. It shows a clear ferromagnetic transition at $\sim 70$ K with a saturation magnetization within uncertainty of $7{\mu }_B$/${\mathrm{Gd}}^{3+}$ ion, a remanence of $5{\mu }_B$/${\mathrm{Gd}}^{3+}$ ion, and a coercive field of $\sim 5$ mT. It is doped by $\sim 1$% nitrogen vacancies that introduce $\sim 3\times {10}^{20}{\mathrm{cm}}^{-3}$ electrons into the conduction band. The resistivity shows transport in a conduction band doped to degeneracy by $\sim 0.01$ electrons/formula unit with a residual resistance ratio of 2 and a Hall resistivity permitting easily separated ordinary and anomalous Hall components. The electron transport resides in the strongly spin-split $5d$ conduction band that ensures purely majority-spin transport.

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• Electrical conductivity
• Magnetic semiconductors
• Rare-earth magnetic materials
• Hall bar
• Molecular beam epitaxy