Observation of an unusual field dependent slow magnetic relaxation and two distinct transitions in a family of new complexes

Abstract

An unusual field dependent slow magnetic relaxation and two distinct transitions were observed in a family of new rare earth-transition metal complexes, [Ln (bipy) (H${}_2$O)${}_4$ M(CN)${}_6$] $\cdot$1.5 (bipy) $\cdot$ 4H${}_2$O (bipy = 2,2'-bipyridine; Ln = Gd${}^{3+}$,Y${}^{3+}$; M = Fe${}^{3+}$, Co${}^{3+}$). The novel magnetic relaxation, which is quite different from those in normal spin glasses and superparamagnets but very resembles qualitatively those in 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 DC and AC susceptibility as well as heat capacity measurements.

Revtex, 6 figures