On the participation of domains in the high spin (5T2) ⇄ low spin (1A1) transition in dithiocyanatobis (2,2′-bi-2-thiazoline) iron (II)

The hysteresis in the high spin ⇄ low spin transition of [Fe(bt)2(NCS)2] (bt=2,2′-bi-2-thiazoline) has been studied by magnetic susceptibility measurements in two different preparations and in a mechanically treated (ball mill) sample. From the measurement of two inner hysteresis loops and a comparison with Everett’s theorems for hysteresis effects, it could be established that independent domains (i.e., groups of complex molecules of like spin that can only change their state simultaneously) participate in the spin transition in the unperturbed sample. The domains were found to be no longer independent in the milled sample. This property may result from a different limitation in the size of the domains caused by lattice defects as compared to the unperturbed sample.