Interpretation of 53Cr3+ electron–nuclear double resonance data obtained in hydrated crystals in terms of vibrational and static crystal distortion contributions to the spin Hamiltonian parameters. II

Publisher Website
Google Scholar
Abstract
Electron nuclear double resonance (ENDOR) measurements of 53Cr3+ are extended to more isomorphs of guanidinium aluminum sulfate hexahydrate (GAlSH) and the alums. This is done because a satisfactory analysis of the varied ENDOR data obtained in the crystals can be obtained only by studying families of crystal isomorphs. An important relationship obtained in the combined double resonance studies at 4.2 °K is a plot of the quadrupole hyperfine parameter Q′ vs the zero field splitting parameter D. It is found that the Q′ points fall on a series of straight horizontal lines, indicating that Q′ is independent of D. The simple theory shows that if the trigonal distortion in the Cr3+⋅6H20 magnetic complexes is due to static effects alone then a direct proportionality between Q′ and D is expected. It is possible to give a satisfactory explanation to the experimental Q′ vs D diagram if the vibrational effect of the crystals is assumed to play an essential role. An analysis of the vibrational and static crystal distortion contributions to Q′ and D can be done in a consistent manner if the D vs T curves obtained in the crystals are also considered. Consequently both the Q′ vs D and D vs T plots can be explained separately, and a description of the physical behavior of the crystals made.