Site-selective magnetic order of neptunium inNp2Ni17

Abstract

We present the results obtained by superconducting quantum interference device (SQUID) magnetometry, specific heat, and Mössbauer spectroscopy measurements carried out on Np 2 Ni 17 polycrystalline samples. We show that long-range magnetic order, with a moment μ (2b) ∼ 2.25 μ B , occurs below T N = 17.5 K on the Np (2b) sites. A nontrivial situation is observed in that the other Np sites (2d) do not take part to the order transition and carry only an induced moment of about 0.2 μ B below T N . A combined analysis of the different experimental data sets allowed us to determine key parameters associated with the electronic structure of the system. The experimental results are discussed against first-principles electronic structure calculations based on the spin-polarized local spin density approximation plus Hubbard interaction.

Synthesis and properties of AxV2Al20 (A = Th, U, Np, Pu) ternary actinide aluminides

“…No sign of nuclear Schottky anomaly, commonly found for the Np-based intermetallic compounds well above 2 K [46][47][48][49], was observed in C p (T), suggesting that the magnetic hyperfine fields acting on Np nuclei are weak. This is in agreement with the delocalized character of Np 5f electrons.…”

Synchrotron Radiation Techniques and their Application to Actinide Materials

“…A good example of the utility of the XMCD technique in considering a complex material, about which little was known previously, is the study of Np 2 T 17 (T = Co, Ni), where the unit cell contains two different Np sites and site-selective magnetic order can occur (Halevy et al, 2012;Hen et al, 2015). By combining XMCD with Mössbauer 237 Np spectroscopy, magnetization measurements, and first principles electronic structure calculations a deep insight on the ground state of these Np intermetallics was obtained.…”