Rare-earth ion-assisted nuclear spin-lattice relaxation inNd3+-doped binary sodium borate glasses: B11NMR study

Abstract

Rare-Earth (RE) doped glasses are promising candidates for laser and other opto-electronic applications. The optical properties of the RE doped glasses depend on the symmetry and environment of the RE ion in the host glass and hence its structure. We have studied ${\mathrm{Nd}}^{3+}$ doped $30{\mathrm{Na}}_{2}\mathrm{O}\text{\ensuremath{-}}(70\text{\ensuremath{-}}x){\mathrm{B}}_{2}{\mathrm{O}}_{3}\text{\ensuremath{-}}x{\mathrm{Nd}}_{2}{\mathrm{O}}_{3}$ glasses with various ${\mathrm{Nd}}^{3+}$ concentrations $(x=0,0.1,0.5,1\phantom{\rule{0.3em}{0ex}}\mathrm{mol}%)$ using $^{11}\mathrm{B}$ NMR. In this paper we have presented a method of estimating the crystal field splitting of the RE ion using $^{11}\mathrm{B}$ Nuclear Spin-Lattice Relaxation (NSLR) time measurements in these systems as a function of temperature in the range $100--4.2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Details of the magnetization recovery fit, theory of $^{11}\mathrm{B}$ relaxation time are discussed in terms of possible relaxation mechanisms in the presence of a RE ion. We found that the relaxation can be explained using a two-level system (TLS) model for $x=0$ and the Orbach process for other samples. The magnetization recovery is observed to fit better to a single exponential model in all the samples as evident from the statistical analysis of the fit. The crystal field splitting $(\ensuremath{\Delta})$ estimated from our studies are found to be around $100\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$, in agreement with other ${\mathrm{Nd}}^{3+}$-doped systems reported in the literature.