Far-Infrared Stark and Zeeman Splitting of Pr3+, Nd3+, Er3+, Ho3+, and Dy3+ in Some Lanthanide Fluorides

Abstract

The Zeeman effect has been studied in several rare-earth ions imbedded in lanthanide fluorides. A special cryostat has been constructed with two liquid-helium tanks. One, at 4 K, contains a superconducting coil giving magnetic fields as high as 60 kOe. The other, at 1.3 K, contains a Ge:Ga bolometer to detect far-infrared radiation. Large splittings, as high as 30 ${\mathrm{cm}}^{-1\mathrm{}}$, have been observed with ${\mathrm{Nd}}^{3+}$, ${\mathrm{Er}}^{3+}$, and ${\mathrm{Dy}}^{3+}$ where the ground state is a Kramers doublet. For ${\mathrm{Pr}}^{3+}$ and ${\mathrm{Ho}}^{3+}$, which do not give Kramers doublets, the effect of a magnetic field is not so significant. The effect is negligible for ${\mathrm{Pr}}^{3+}$. For ${\mathrm{Ho}}^{3+}$, a 3-${\mathrm{cm}}^{-1\mathrm{}}$ shift and a line broadening are observed. On the other hand, whereas the spectra of Na${\mathrm{F}}_3$: ${\mathrm{Nd}}^{3+}$ and Nd${\mathrm{F}}_3$ are very similar, for Pr${\mathrm{F}}_3$ a pair of ions seems to be present and gives twice as many electronic lines compared to Na${\mathrm{F}}_3$: ${\mathrm{Pr}}^{3+}$. Localized modes are observed close to 73 ${\mathrm{cm}}^{-1\mathrm{}}$ for both ${\mathrm{Er}}^{3+}$ and ${\mathrm{Dy}}^{3+}$, while an absorption band is observed at 64 ${\mathrm{cm}}^{-1\mathrm{}}$ for ${\mathrm{Dy}}^{3+}$ which seems to be slightly sensitive to the magnetic field and has still to be explained. An average spectroscopic $g$ value for the ground-state and first-excited-state Kramers doublet has been calculated for ${\mathrm{Nd}}^{3+}$, ${\mathrm{ER}}^{3+}$, and ${\mathrm{Dy}}^{3+}$. For the ground-state Kramers doublet, these values are well within the limits of the reported $g$ tensor based upon ESR. For the first-excited-state Kramers doublet the determinations are, respectively, $g_2=1.7, 3.6, \mathrm{and} 11.5$ and they constitute new data.