Semimetallic Paramagnetic Nano‐Bi 2 Ir and Superconducting Ferromagnetic Nano‐Bi 3 Ni by Microwave‐Assisted Synthesis and Room Temperature Pseudomorphosis

Uniform nanocrystals of the intermetallic compounds Bi 2 Ir (diameter ≥ 50 nm) and Bi 3 Ni (typical size 200 × 600 nm) were obtained by a microwave‐assisted polyol process at 240 °C. The method was also applied to the spatially confined reaction environment in the microporous exo ‐template SBA‐15 resulting in Bi 3 Ni particles of about 6 nm. Non‐crystalline bundles of parallel Bi 3 Ni nanofibres that have an individual diameter of less than 1 nm were obtained by reductive pseudomorphosis of the subiodide Bi 12 Ni 4 I 3 at room temperature. Magnetic susceptibility measurements demonstrate coexistence of ferromagnetism and superconductivity in a single phase for the nanostructured Bi 3 Ni materials. Curie temperature, coercive field, remnant magnetization, saturation moment, diamagnetic screening, and critical field vary with particle size. The crystal structure of Bi 2 Ir was determined by Rietveld refinement of powder X‐ray diffraction data. Bi 2 Ir crystallizes in the monoclinic arsenopyrite type (space group P 2 1 / c ), a superstructure of the markasite type, with a = 690.11(1), b = 678.85(1), c = 696.17(1) pm, and β = 116.454(1)°. In contrast to most of the other phases of this type, the Bi 2 Ir is not a diamagnetic semiconductor but a weakly paramagnetic semimetal. Conductivity measurements down to 4 K and magnetization measurements in a field of μ 0 H = 10 mT down to 1.8 K give no evidence for a transition into the superconducting state. Bonding analysis shows prevailing contribution of Bi–Bi interactions to the conduction, whereas Bi–Ir bonding is mostly covalent and localized.