AgII-containing phases of the form A2AgF4 or AAgF3 (A = K, Rb, Cs) have previously been synthesized via solid state reaction by us and others; Cs2AgF4 is structurally related to K2NiF4 and shares structural similarities with other strongly correlated structures, including the high Tc cuprates. The magnetic behavior of these materials shows that the spins associated with the 4d9 AgII ions are stron ...