RESUMO
The novel iridate Ba8Al2IrO14 was prepared as single crystals by self-flux method, thereby providing a rare example of an all-Ir(VI) compound that can be synthesized under ambient pressure conditions. The preparation of all-Ir(6+) iridate without using traditional high-pressure techniques has to our knowledge previously only been reported in Nd2K2IrO7 and Sm2K2IrO7. The monoclinic crystal structure (space group C2/m, No.12) is stable down to 90 K and contains layers of IrO6 octahedra separated by Ba and AlO4 tetrahedra. The material exhibits insulating behavior with a narrow band gap of â¼0.6 eV. The positive Seebeck coefficient indicates hole-like dominant charge carriers. Susceptibility measurement shows antiferromagnetic coupling with no order down to 2 K.
RESUMO
Magnetism has been predicted to occur in systems in which dipolar interactions dominate exchange. We present neutron scattering, specific heat, and magnetic susceptibility data for LiErF(4), establishing it as a model dipolar-coupled antiferromagnet with planar spin-anisotropy and a quantum phase transition in applied field H(c|| = 4.0 ± 0.1 kilo-oersteds. We discovered non-mean-field critical scaling for the classical phase transition at the antiferromagnetic transition temperature that is consistent with the two-dimensional XY/h(4) universality class; in accord with this, the quantum phase transition at H(c) exhibits three-dimensional classical behavior. The effective dimensional reduction may be a consequence of the intrinsic frustrated nature of the dipolar interaction, which strengthens the role of fluctuations.