Electron paramagnetic resonance of Fe3+ in guanidinium aluminum sulfate hexahydrate

Abstract

The electron paramagnetic resonance spectrum of Fe3+ substituted for Al3+ in guanidinium aluminum sulphate hexahydrate, C(NH2)3 Al(SO4)2⋅6H2O, is measured at X-band frequencies at room, liquid nitrogen, and liquid helium temperatures. The measurements are made for various orientations of the magnetic field. The values of all the parameters are deduced from the data using a rigorous least-squares fitting procedures, in a simultaneous fitting of the data corresponding to several orientations of the magnetic field. The zero-field splitting parameter b02, as determined from liquid helium data, is found to have a negative sign. In particular, the following values for the g tensor and b02 are found. At 295 K, for site I gzz=2.001±0.003, gxx =2.004±0.003, b02=−8.622 ±0.008 GHz; for site II gzz=2.002±0.003, gxx=2.002±0.003, b02=−8.499±0.008 GHz. At 1.61 K, for site I gzz =1.994±0.003, gxx=1.992±0.003, b02=−8.931 ±0.008 GHz; for site II gzz=1.996±0.003, gxx =1.997±0.003, b02=−8.808±0.008 GHz.