Anisotropic magnetic phase diagram of geometrically frustrated iridate Ca[formula omitted]Ir[formula omitted]O12.

We report magnetic properties of single-crystal Ca 5 Ir 3 O 12 having a hexagonal noncentrosymmetric structure. We measured the anisotropy of the magnetic phase transition at 7.8 K up to 70 kOe and obtained magnetic phase diagrams parallel and perpendicular to the c -axis. The magnetic phase diagrams showed that the transition temperature was gradually suppressed on application of a magnetic field to perpendicular to the c -axis. In contrast, the transition temperature was increased when a magnetic field of up to 70 kOe was applied to the c -axis. We examined this enhancement in the magnetic transition temperature along the c -axis. From these features of the observed magnetic properties, possibility of multipole magnetic ordering was examined. • Magnetic moments of Ir4+ are aligned in the c -plane of its triangular sublattice. • Van Vleck susceptibility derived from Ir5+ is highly anisotropic. • The magnetic ordered temperature along the c -axis is enhanced. • A multipole magnetic order is considered from the magnetic phase diagram. [ABSTRACT FROM AUTHOR]