Magnetic properties of neptunium Laves phases:NpOs2−xRuxpseudobinary system

The magnetic properties of the $\mathrm{Np}{\mathrm{Os}}_{2-x}{\mathrm{Ru}}_x$ pseudobinary system ($C-15\mathrm{}$ Laves-phase structure) have been investigated by magnetization, resistivity, and nuclear-$\gamma$-ray resonance measurements between 1.6 and 300 K. The regular variation of magnetic properties with neptunium-neptunium distance $d_{\mathrm{Np}}$ seen in the binary neptunium Laves phases extends into the pseudobinary system. All the compounds studied here appear to order ferromagnetically with a transition temperature ($T_C\le 5$ K for $x\ge 0.4$) that decreases with an increase in $x$. The magnetic behavior is interpreted in terms of an increase in delocalization of the magnetic $5f$ electrons as $d_{\mathrm{Np}}$ decreases.