Orbital Angular Momentum-Driven Ferromagnetism with Magnetic Anisotropy and Electronic Structure of Epitaxial Neodymium Nitride.

Neodymium-based permanent magnets are fundamental to modern technologies, underpinning high-performance applications in electronics, renewable energy, and advanced medical systems. Among emerging neodymium compounds, neodymium nitride (NdN) has attracted significant attention due to its unique electronic structure, where strongly localized 4f orbitals and strong spin-orbit coupling are anticipated to drive exceptional magnetic behavior. Here, we show conclusive experimental evidence of orbital angular momentum-driven ferromagnetic ordering and prominent magnetic anisotropy in epitaxial, near-stoichiometric NdN thin films synthesized using ultrahigh vacuum deposition techniques. Magnetization and X-ray magnetic circular dichroism measurements reveal a dominant 4f orbital moment of 5.14 μB, contributing to a total magnetic moment of 2.43 μB per formula unit at 4 K, close to the first-principles density functional theory calculated values. Complementary synchrotron-radiation photoelectron spectroscopy, along with the theoretical calculations, uncovers occupied 4f states ∼6.4 eV below the Fermi level, contributing to the orbital-driven ferromagnetism in NdN. Moreover, the high crystalline quality of the NdN films is further supported by the structural characterization and vibrational properties. The intrinsic orbital angular momentum-driven magnetism of NdN positions it as a promising platform for next-generation orbitronic devices beyond conventional spintronics.