Negative thermal expansion and antiferromagnetism in the actinide oxypnictide NpFeAsO

Abstract

A neptunium analogue of the LaFeAsO tetragonal layered compound has been synthesized and characterized by a variety of experimental techniques. The occurrence of long-range magnetic order below a critical temperature T_N = 57 K is suggested by anomalies in the temperature-dependent magnetic susceptibility, electrical resistivity, Hall coefficient, and specific heat curves. Below T_N, powder neutron diffraction measurements reveal an antiferromagnetic structure of the Np sublattice, with an ordered magnetic moment of 1.70(0.07) μ_B aligned along the crystallographic c-axis. No magnetic order has been observed on the Fe sublattice, setting an upper limit of about 0.3 μ_B for the ordered magnetic moment on the iron. High resolution x-ray powder diffraction measurements exclude the occurrence of lattice transformations down to 5 K, in sharp contrast to the observation of a tetragonal-to-orthorhombic distortion in the rare-earth analogues, which has been associated with the stabilization of a spin density wave on the iron sublattice. Instead, a significant expansion of the NpFeAsO lattice parameters is observed with decreasing temperature below T_N, corresponding to a relative volume change of about 0.2% and to an invar behavior between 5 and 20 K. First-principle electronic structure calculations based on the local-spin density plus Coulomb interaction and the local density plus Hubbard-I approximations provide results in good agreement with the experimental findings.

arXiv commentAccepted for publication in Phys. Rev. B

References in corpus (16)

• Anomalous Hall effect
• LaFeAsO${}_{1-x}$F${}_x$: A low carrier density superconductor near itinerant magnetism
• Nature of the 5f states in actinide metals
• Implementation of the LDA+U method using the full potential linearized augmented plane wave basis
• Magnetism in Fe-based superconductors
• Electron Correlations in the Low Carrier Density LaFeAsO0.89F0.11 Superconductor (Tc = 28 K)
• Magnetism, Spin-Orbit Coupling, and Superconducting Pairing in UGe${}_2$
• Lattice and Magnetic structures of PrFeAsO, PrFeAsO0.85F0.15 and PrFeAsO0.85
• Influence of the rare-earth element on the effects of the structural and magnetic phase transitions in CeFeAsO, PrFeAsO, and NdFeAsO
• Magnetic Ordering and Negative Thermal Expansion in PrFeAsO
• Electronic structure and spectral properties of Am, Cm and Bk: Charge density self-consistent LDA+HIA calculations in FP-LAPW basis
• Strong coupling of Sm and Fe magnetism in SmFeAsO as revealed by magnetic x-ray scattering
• Theory of Anomalous Hall Effect in a Heavy fermion System with a Strong Anisotropic Crystal Field
• Quantum Oscillation Studies of the Fermi Surface of LaFePO
• Systematic Study on Fluorine-doping Dependence of Superconducting and Normal State Properties in LaFePO1-xFx
• Fe-based superconductors: unity or diversity?

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• Thermal Expansion of the Heavy-fermion Superconductor PuCoGa${}_5$
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