Field-dependent ordered phases and Kondo phenomena in the filled skutterudite compound PrOs₄As₁₂

Electrical resistivity, specific heat, and magnetization measurements to temperatures as low as 80 mK and magnetic fields up to 16 T were made on the filled skutterudite compound PrOs₄AS₁₂. The measurements reveal the presence of two ordered phases at temperatures below approximately 2.3 K and in fields below approximately 3 T. Neutron-scattering experiments in zero field establish an antiferromagnetic ground state <2.28 K. In the anti-ferromagnetically ordered state, the electronic-specific heat coefficient γ ≈ 1 J/mol·K² below 1.6 K and 0 ≤ H ≤ 1.25 T. The temperature and magnetic-field dependence of the electrical resistivity and specific heat in the paramagnetic state are consistent with single-ion Kondo behavior with a low Kondo temperature on the order of 1 K. The electronic-specific heat in the paramagnetic state can be described by the resonance-level model with a large zero-temperature electronic-specific heat coefficient that decreases with increasing magnetic field from approximately 1 J/mol·K² at 3 T to approximately 0.2 J/mol·K ² at 16 T.