Large exchange bias and low-temperature glassy state in the frustrated triangular-lattice antiferromagnet Ba3NiIr2O9

Here, we report both ac and dc magnetization, thermodynamic, and electric properties of hexagonal Ba3NiIr2O9. Ni2+ (spin 1) forms a layered triangular lattice and interacts antiferromagnetically, while Ir5+ is believed to act as a magnetic link between the layers. This complex magnetic interaction results in magnetic frustration, leading to a spin-glass transition at T-f similar to 8.5 K. The observed magnetic relaxation and aging effect also confirm the nonequilibrium ground state. The system further shows large exchange bias which is tunable with cooling field. Below the Curie-Weiss temperature theta(CW) (similar to - 29 K), the magnetic specific heat C-m displays a broad hump and at low temperature follows C-m = gamma T-alpha dependence, where both gamma and alpha show dependence on temperature and magnetic field. A sign change in magnetoresistance is observed which is due to an interplay among the magnetic moment, field, and spin-orbit coupling.

Automated summary

In this study, the magnetic, thermodynamic, and electric properties of hexagonal Ba3NiIr2O9 were investigated. The interactions between Ni2+ and Ir5+ resulted in complex magnetic frustration and a spin-glass transition, showing a nonequilibrium ground state. The system exhibited large exchange bias and specific thermodynamic behaviors at low temperatures.