Frustrated local moment magnetism in a metallic system: Ce₆Ni₆P₁₇

Frustrated metallic systems are potentially of strong interest because the interaction between magnetic and itinerant degrees of freedom is expected to result in unusual properties. However the number of appropriate systems is extremely scarce. Because of its structure the polyphosphide Ce₆Ni₆P₁₇ is an attractive candidate. Ce atoms are located on the corners of octahedra, which form a body centered cubic lattice. Thus one might expect frustration within the octahedra and frustration because of the body centered arrangement of the octahedra. A preliminary study provided some evidence for frustration, but presented only limited experimental results. We synthesized polycrystalline samples and present magnetization, specific heat and resistivity data. Our results confirm Ce₆Ni₆P₁₇ to be a metallic, frustrated local moment system. Kondo interaction are negligible resulting in well-defined 4f local moments. Specific heat C(T)/T data evidence magnetic order at merely T_N = 0.97 K, with only a small anomaly at T_N compensated by a huge tail in C(T)/T extending far above T_N. The magnetic fluctuations indicated by this large tail in C(T)/T are also seen as a broad maximum in χ(T) at T > T_N. Thus Ce₆Ni₆P₁₇ is a very promising candidate for studying magnetic frustration in a metallic system.