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) ·4H₂O (bipy0ex0ex=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 Mn₁₂-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.