Multipleswitchable physical properties have been demonstrated in one single niccolitestructural metal–organicframework, [(CH3CH2)2NH2][FeIIIFeII(HCOO)6] (1), including (i) a reversibleferroelastic phase transition triggered by freezing the disordered (CH3CH2)2NH2+cations, (ii) a thermally switchable dielectric constant transition accompaniedby phase transition, and (iii) thermal and positive magnetic field drivenmagnetic poles reversal at low temperatures, attributed to different responsesof the magnetization of FeII and FeIII sublattices to external stimuli. Moreinterestingly, the exchange anisotropy between the two sublattices can alsogive rise to tunable positive and negative exchange bias fields.Straightforwardly, such diverse demonstrations of bistability in one singlematerial (depending on the specific tuning way) will provide extra freedom andflexibility for the design of switcher devices.
