Effects of Applied Electric Fields on Paramagnetic Resonance in Chrome Alums

Abstract

The paramagnetic resonance spectra of single crystals of potassium chrome alum and ammonium chrome alum have been investigated in the presence of applied electric fields at 9.3 kMc/sec in the temperature range 4-300°K. The measurements were made in an effort to detect the possible existence of a term of the form $\xi {\mu }_0\sigma ·\mathrm{E}$ in the interaction Hamiltonian for an electron in an electromagnetic field. Such a term corresponds to the existence of an electron electric dipole moment and would result in a lifting of Kramers' degeneracy for a magnetic ion in a crystalline field. No such term was observed, and the upper limit on $\xi$ obtained was $\xi <0.007\mathrm{}$. A dependence of the dielectric loss on electric field was observed in both alums at microwave frequencies.