Observation of an unusual field-dependent slow magnetic relaxation and two distinct transitions in a family of rare-earth-transition-metal complexes

An unusual field-dependent slow magnetic relaxation and two distinct transitions were observed in a family of rare-earth-transition-metal complexes [Ln (bipy) (H2O)(4) M(CN)(6)] . 1.5 (bipy) . 4H(2)O (bipy = 2,2'-bipyridine; Ln = Gd3+,Y3+; M = Fe3+, Co3+). The magnetic relaxation, which is quite different from those in normal spin glasses and superparamagnets but qualitatively resembles those in the single-molecule magnet Mn-12-Ac even if they possess different structures, might be attributed to the presence of frustration that is incrementally unveiled by the external magnetic field. The two distinct transitions in [GdFe] were presumed from de and ac susceptibility as well as heat capacity measurements.