MAGNETIC-PROPERTIES OF RUF5

The structural unit of the pentafluorides MF5 (M = Ru, Rh, Os, Ir, Pt) consists of M4F20 tetramers with the transition elements occupying the corners of the rhombus. In the case of RuF5 the magnetic susceptibility vs. temperature curve shows a broad maximum at T {reversed tilde equals} 40 K. Neutron diffraction experiments below and above this temperature show that this maximum does not correspond to a magnetic three-dimensional ordering. Theoretical calculations based on isolated tetra-nuclear clusters of identical S = 3 2 spins have been applied. The intracluster exchange interactions are antiferromagnetic. The fitting of the susceptibility data leads to an exchange constant of J k = -8.3 K. © 1979.