EPR evidence of possible metastable regions in Mn2+ doped ferroelectric NaNO2

Of the various EPR spectra observed in the ferroelectric phase of NaNO2, a spectrum designated as spectrum II is observed to have some peculiar properties like dependence of its intensity on growth conditions of the crystal, its disappearance below ≈60°C after heat treatment of the crystal, its reappearance by heating above ≈60°C and also by application of an external dc electric field at ≈30°C. These observations suggest the possible existence, around Mn2+-vacancy complex in the ferroelectric phase of NaNO2, of a metastable structure intermediate to the paraelectric and ferroelectric phase structures.