Quantum and Other Oscillations of the Nuclear Spin-Lattice Relaxation Rate inn−InSb

Abstract

Measurements of the nuclear spin-lattice relaxation rate $\frac{1}{T_1}$ for ${\mathrm{In}}^{115}$, ${\mathrm{Sb}}^{121}$, and ${\mathrm{Sb}}^{123}$ in $n$-type InSb at low temperatures (1.3-4.2°K) are presented as a function of magnetic field $H$ and crystal orientation for several conduction-electron concentrations in the range 2×${10}^{14}$ to 1.2×${10}^{16}$ ${\mathrm{cm}}^{-3\mathrm{}}$. The observed relaxation rate is separated into four components, primarily on the basis of their magnetic field dependence. Three components exhibit sharp peaks in the variation of $\frac{1}{T_1}$ with magnetic field, whereas the fourth component appears as a smoothly varying background. One of the peaked components is identified as quantum oscillations (QO) in $\frac{1}{T_1}$. As in the case of analogous phenomena, such as the de Haas—van Alphen effect, they are caused by the oscillations in the density of conduction-electron states at the Fermi energy which occur when the magnetic field is varied. The other peaks, of an as yet undetermined origin, are labeled type-A and type-B peaks. They occur at values of the magnetic field above that at which the last QO should occur. Explicit calculations of some of the properties of the QO in the limit of low temperatures are also presented.