Partially disordered state with short-range spin correlation in S=5/2 classical triangular antiferromagnet Ag_{2}FeO_{2}

Abstract

A triangular-lattice antiferromagnet of Ag_{2}FeO_{2} was synthesized under high pressure. Its magnetism was studied in terms of electrical resistivity, magnetic susceptibility, heat capacity, powder neutron scattering, and Mössbauer spectroscopy. The magnetic state of Ag_{2}FeO_{2} changes successively through a second-order phase transition at T_{p}=36 K and a crossover at T_{c}=20 K. A partially disordered (PD) state appears below T_{p}, in which ≈2/3 spins are ordered and the remaining ≈1/3 spins fluctuate, which state persists at least down to 5 K. The spin correlation length starts to grow at T_{p}; however, it remains very short (≈27 Å) below T_{c}. This exotic magnetism is concerned with strong frustration in the classic antiferromagnetic triangular lattice.