抄録
Electron paramagnetic resonance of Mn2+ in a single crystal of tris-sarcosine calcium bromide (TSCBr), as a function of temperature and orientation, has been studied. These studies suggest the existence of two chemically equivalent but physically non equivalent Mn2+ site in a unit cell of TSCBr. Of the two space groups determined by neutron diffraction studies, Pnma and Pn21a, EPR studies are in conformity with the space group Pnma. The dielectric constant measurements in TSCBr do not show any anomaly in the temperature interval 300–100 K. Tris-sarcosine calcium chloride (TSCC, space group Pnma in the paraelectric phase) undergoes a ferroelectric phase transition at 127 K. Replacement of Cl by Br is expected to introduce changes in the N-H..X bond (X=Cl, Br) and hence, we believe, protons in the N-H..Cl bond may be playing an important role in the mechanism of ferroelectricity in TSCC.
