Theoretical and experimental studies in electron paramagnetic resonance I: an investigation of the 290K angular spectra of gadolinium (Gd3+, 8s) in Lanthanum Ethyl Sulphate at 5, 10 and 35 GHz using Conventional and generalized Spin-Hamiltonians

Abstract

The phenomenon of electron paramagnetic resonance is described microscopically using the rotating.codrdinate methodand macroscopically using the Bloch formalism. Two major nonradiative physical processes, the spin-lattice and spin-spin interactions, whereby a paramagnetic system can loose energy to its environment are briefly discussed. A qualitative description of the crystal-field theory is given. The spin-C Hamiltonian formalism developed by Abragam and Pryce (1951) for interpreting paramagnetic resonance experimental results is described. The conventional (Bleaney, etal., 1951) and generalized spin-Hamiltonian (Grant and Strandberg, 1964) for gadolinium, in lanthanum ethyl sulphate, arederived. The proposed mechanisms for interpreting:the splittingof the ground 8S state of Gd 3+ are reviewed. The EPR spectra of 0.1 per cent Gd 3 as a paramagnetic impurity in lanthanum ethyl' -sulphate were measured at'290°K using 5,10 and 35GHz. spectrometers which, are described. ,The parameters in the conventional:, and genèralizedspin-,Hamiltohian for,' Gin Ianthanum.ethyl, sü1hate were determined at directions parallel and perpendicuThr to lhe cry.sta1 :y 'metry axis using the 5, lQ and35GHz EPR spectra of AM = ± 1 transitions. 'A'convergent, least-mean-square.on1pUter method was utilized for the •àalculation. The eperi.mental and calculated-angular spectra of M = ± 1 and AM =± 2 transitions,are presehted. The experimental results and calculation methods are discussed.