Nuclear Quadrupole Resonance and Electron Spin Resonance in C(NH2)3Al(SO4)2·6H2O and Isomorphous Compounds

Abstract

The temperature dependence of the nuclear quadrupole coupling parameters, $\frac{\mathrm{eQq}}{h}$, of Al and Ga has been measured in the ferroelectric compound C${\left(\mathrm{N}{\mathrm{H}}_2\right)}_3$Al${\left(\mathrm{S}{\mathrm{O}}_4\right)}_2$·6${\mathrm{H}}_2$O (GAlSH) and three other isomorphous compounds that result when Ga replaces Al and Se${\mathrm{O}}_4$ replaces S${\mathrm{O}}_4$. Measurements were also made on deuterated GAlSH. The temperature dependence of the electron spin resonance (ESR) of ${\mathrm{Cr}}^{3+}$, substituted for Al or Ga in the above five compounds, was also measured. For the five compounds, $\frac{\mathrm{eQq}}{h}$ versus temperature for each compound was similar, small (∼100 kc/sec), linear with temperature, and in some cases changed sign. Within the framework of the ionic model, $\frac{\mathrm{eQq}}{h}$ and $\frac{d\left(\frac{\mathrm{eQq}}{h}\right)}{\mathrm{dT}}$ have been calculated. It is found that the latter is fairly insensitive to the x-ray and charge distribution parameters and depends mainly on the large anisotropic thermal expansion coefficient. Using the theoretically calculated antishielding factor, there is agreement between the calculated and the measured $\frac{d\left(\frac{\mathrm{eQq}}{h}\right)}{\mathrm{dT}}$. The data also indicate that the ratio of the antishielding factors of ${\mathrm{Al}}^{3+}$ and ${\mathrm{Ga}}^{3+}$ are in approximate agreement with the calculated values.