Spin Lattice Relaxation in Neodymium Ethylsulphate at Liquid Helium Temperatures

The optical Faraday effect was used to measure instantaneous magnetization in neodymium ethylsulphate. The spin populations were disturbed by pulses of microwave power, and by adiabatic magnetization and demagnetization, and the approach to equilibrium was studied. The relaxation was found to be exponential and spin lattice relaxation times were measured, for temperatures between 1.3° K and 4.2° K, and for magnetic fields between 80 and 6000 oersted. The relaxation time was found to decrease with increasing magnetic field, and to vary with temperature approximately as 1/T 3 . No dependence of relaxation time on pulse length was found.