Influence of the transition-metal substitution on the physical properties of Lu2−xNi21B6 – From Pauli-paramagnetism to weak ferromagnetism

The ternary boride Lu2−xNi21B6 crystallizes with the Cr23B6 structure type (space group Fm 3 ¯ m, a = 10.6256(2)). It is a Pauli paramagnet with a rather large temperature-independent contribution of χ0 = 1.7 × 10−3 emu/mol and an effective moment μeff = 1.5 μB/f.u. Density functional calculations performed for Lu2Ni21B6 showed that hole doping could lead to band magnetism, while light electron doping should suppress the tendency toward magnetic order. Both predictions are confirmed experimentally: Lu1.65Ni17.5Co3.5B6 is a weak itinerant soft ferromagnet with TC ≈ 39 K, an effective paramagnetic moment μeff = 5.86 μB/f.u., and a Weiss temperature θW = +71 K, while Lu1.65Ni20.75Cu0.25B6 and Lu1.35Y0.3Ni21B6 are Pauli paramagnets with rather small Curie-like contributions at low temperatures.