Abstract:
We consider the electronic structure of, and magnetic exchange spin interactions between, nominally nonmagnetic Eu3+ ions 4f 6, S=3, L=3, J=0 within the context of the rocksalt structure compounds EuN and EuP. Both compounds are ionic Eu3+; N3− and P3− semimetals similar to isovalent GdN. Treating the spin polarization within the 4f shell, and then averaging consistent with the J=0 configuration, we estimate semimetallic band overlaps Eu 5d with pnictide 2p or 3p of 0.1 eV EuN and 1.0 eV EuP that increase become more metallic with pressure. The calculated bulk modulus is 130 86 GPa for EuN EuP. Exchange spin-spin coupling calculated from correlated band theory is small and ferromagnetic in sign for EuN, increasing in magnitude with pressure. Conversely, the exchange coupling is antiferromagnetic in sign for EuP and is larger in magnitude, but decreases with compression. Study of a two-site model with S 1 ·S 2 coupling within the J=0,1 spaces of each ion illustrates the dependence of the magnetic correlation functions on the model parameters, and indicates that the spin coupling is sufficient to alter the Van Vleck susceptibility. We outline a scenario of a spin-correlation transition in a lattice of S=3, L=3, J=0 nonmagnetic ions.
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