Anomalous nuclear spin-lattice relaxation of $^3\mathrm{He}$ in contact with ordered $\mathrm{Al_2O_3}$ aerogel

Spin-lattice relaxation of $^3\mathrm{He}$ in contact with the ordered $\mathrm{Al_2O_3}$ fiber aerogel has been studied at the temperature of $1.6$ K in fields of $0.1$–$0.5$ T by the pulsed nuclear magnetic resonance (NMR) method. An additional mechanism of the relaxation of $^3\mathrm{He}$ in aerogels is found and it is shown that this relaxation mechanism is not associated with the adsorbed layer. A hypothesis about the influence of intrinsic paramagnetic centers on the relaxation of gaseous $^3\mathrm{He}$ is proposed.