Electronic Structure and Magnetic Character of Antiferromagnetic Compound NpPt₂In₇

A very important class of materials, the A_nM_mIn_3n+2m family, where M is a group 9 transition metal and A=Ce, U, Np or Pu, offers to explore the relationship between unconventional superconductivity and magnetism. In this work, we present a theoretical study of a Np-based member of this family, an antiferromagnetic compound NpPt₂In₇, analogue of heavy-fermion superconductor under pressure CePt₂In₇. We focus on its electronic structure and determine computationally the magnetic character. Calculations were performed in the framework of the relativistic density functional theory (including the spin-orbit coupling) plus Coulomb-U (DFT+SOC+U) using a full-potential linearized augmented plane-wave (FP-LAPW) basis. DFT(+SOC) yields the correct antiferromagnetic (AF) ordering, but fails to reproduce the experimentally observable 2.53 µ_B magnetic moment on Np. The correlated method DFT+SOC+U(AMF) improves the Np-atom magnetic moment over DFT. Also, the calculations produce the AF ground state in agreement with experiment. It indicates fairly localized character of the Np-f-shell in NpPt₂In₇.