EPR Study of the Structure of CsPbCl3

Studies of the EPR of dilute Mn2+ in CsPbCl3 have been carried out over the temperature range 77°–340°K. Crystalline phase changes as indicated by changes in the Pb site symmetry were evident at 320°K (46.5°C) and 185°K. The first of these has been reported previously while the latter is apparently a new observation. Between 185° and 320°K, the EPR spectra can be assigned to two and possibly four crystallographically equivalent sets of magnetically inequivalent sites, the spectra of the ith set derivable from the spin Hamiltonian Hi=gβH·S+Di[Sz2−13S(S+1)]+Ei(Sx2−Sy2)+16ai(Sx4+Sy4+Sz4)+ASzIz+B(SxIx+SyIy). Typical values of the crystal field parameters are: A = −87.5 G, B = −86.5 G, and a≈1 G; all sensibly temperature independent, while D and E are temperature dependent. For example at 195°K, D1,2,3,4=45 G and E1= −E2=7.2 G, E3=6.4 G, and E4= −5.0 G. Both D and E tend continuously to zero at 320°K. Thus, the individual site symmetries are evidently orthorhombic and the overall crystal symmetry is apparently orthorhombic or nearly so. Some discussion of possible crystal space groups is included.