Dependence of Spin-Lattice Relaxation Time Upon Magnetic Field for Two Salts of Neodymium

摘要

Measurements were made below 1.5K of the spin-lattice relaxation rate of Nd(3+) in lanthanum fluoride and lanthanum magnesium nitrate as a function of the separation of the levels of the gound doublet. The relaxation rate for the forbidden transistion was calculated, and it has been shown that under certain circumstances it can be more rapid than the relaxation rate for allowed transitions. There is an additional tribution which depends upon the concentration of Nd(3+) and may be due to cross relaxation to coupled pairs of Nd(3+) ions. In lanthanum magnesium nitrate there is a phonon bottleneck as well as the direct process. Both salts show an Orbach process above 2K. A modification of the usual pulse saturation technique was used to obtain these measurements which gives some advantages over the standard method. (Author)