Ultrasonic Paramagnetic Resonance of Tetravalent Uranium in Calcium Fluoride

摘要

The pulse-echo technique of ultrasonic paramagnetic resonance (UPR) was used at frequencies of 0.47-8.9 gigahertz and liquid helium temperatures to study the spin-lattice interaction between the U(4+) paramagnetic ion and a CaF2 lattice. A spin Hamiltonian is given which considers the effect of random strains on the UPR line shape. A spin-lattice Hamiltonian quadratic in spin and linear in strain was found applicable to the results. The G(ijkl) is the spin-lattice coupling tensor and epsilon kl is the strain due to an ultrasonic vibration. The frequency dependence of the UPR attenuation was studied in the range 1.1 to 8.9 gigahertz. The results agreed with the predicted dependence on frequency squared. The temperature dependence of the UPR attenuation was studied in the range 1.0 to 10.0K. Good agreement was found between the results and the theoretical dependence on 1/T. (Author)