Phase Diagram and NMR Studies of Antiferromagnetically Ordered Polycrystalline Silver

Abstract

We have studied magnetic ordering in the frustrated antiferromagnetic spin-(1/2) system composed of the natural isotopic mixture of silver nuclei. The dynamic susceptibility of polycrystalline foils was measured down to about 0.5 nK (S > 0.4R ln 2) using SQUID-NMR techniques. Two antiferromagnetic resonance branches were observed, which is consistent with ordering into a simple 1-k state. We obtain Tc = (560 ± 60) pK for the transition temperature at B = 0 and Bc = 100 μT for the critical field extrapolated to T = 0.