NMR study of Si-substitution effect for Al in PrTi\(_2\)Al\(_{20}\)

We present the results of \(^{\varvec{27}}\) ${}^{\mathbf{27}}$ Al-nuclear magnetic resonance (NMR) studies of Si-substituted PrTi \(_{\varvec{2}}\) ${}_{\mathbf{2}}$ Al \(_{\varvec{20}}\) ${}_{\mathbf{20}}$ in order to clarify the magnetic and electronic properties at low temperatures and the change by Si substitution for Al from a microscopic point of view. From the analyses of the Knight shift, the hyperfine coupling constants on \(^{\varvec{27}}\) ${}^{\mathbf{27}}$ Al in PrTi \(_{\varvec{2}}\) ${}_{\mathbf{2}}$ (Si \(_{\varvec{0.1}}\) ${}_{\mathbf{0.1}}$ Al \(_{\varvec{0.9}}\) ${}_{\mathbf{0.9}}$ ) \(_{\varvec{20}}\) ${}_{\mathbf{20}}$ are slightly larger than those of PrTi \(_{\varvec{2}}\) ${}_{\mathbf{2}}$ Al \(_{\varvec{20}}\) ${}_{\mathbf{20}}$ . The nuclear spin-lattice relaxation rate \(\varvec{1/T_1}\) $\mathbf{1}\mathbf{/}{\mathit{T}}_{\mathbf{1}}$ does not exhibit any anomaly around 2.0 K, in contrast to the results associated with the quadrupolar ordering in PrTi \(_{\varvec{2}}\) ${}_{\mathbf{2}}$ Al \(_{\varvec{20}}\) ${}_{\mathbf{20}}$ . The analysis of \(\varvec{1/T_1}\) $\mathbf{1}\mathbf{/}{\mathit{T}}_{\mathbf{1}}$ at high temperatures reveals that the \(\varvec{c}\) $\mathit{c}$ – \(\varvec{f}\) $\mathit{f}$ hybridization may be reduced by Si substitution for Al.