Optical study of chromium doped LaGaO3 single crystal

Research on the thermal shifts and electron–phonon coupling parameters of Ri lines for Cr3+ ions in LaGaO3 and LaAlO3 crystals

“…In the measurement, the thermal shifts of two components R 1 and R 2 lines due to the splitting of R line by the low-symmetry crystal field were given (note: may be due to the separation (E5.4 cm À 1 at 1.6 K and 77 K [17][18][19]) between R 1 and R 2 lines in LaAlO 3 :Cr 3 þ being much smaller than that (E 24.1 cm À 1 at 77 K [19]) in LaGaO 3 : Cr 3 þ , the thermal shifts of two components R 1 and R 2 lines for LaAlO 3 :Cr 3 þ have not been reported until now, the R line can therefore be regarded as the average value of R 1 and R 2 lines). Theoretically, they [19,20] found that these thermal shifts of R i lines can be fitted and explained satisfactorily by using the following expression based on the Raman two-phonon process connected with Debye model…”

“…So, the spectroscopic investigations of the doping LaGaO 3 and LaAlO 3 have attracted attention. The optical spectra of LaGaO 3 :Cr 3 þ and LaAlO 3 :Cr 3 þ were measured by some groups [14][15][16][17][18][19][20]. Among them, the thermal shifts (or temperature dependences) of sharp fluorescence R lines (corresponding to the transition 2 E-4 A 2 ) in both crystals were measured by Burns and Jenkins [19].…”

“…Among them, the thermal shifts (or temperature dependences) of sharp fluorescence R lines (corresponding to the transition 2 E-4 A 2 ) in both crystals were measured by Burns and Jenkins [19]. Later on, a more detailed measurement of thermal shift of R line for LaGaO 3 :Cr 3 þ was carried out by Ryba-Romanowski et al [20]. In the measurement, the thermal shifts of two components R 1 and R 2 lines due to the splitting of R line by the low-symmetry crystal field were given (note: may be due to the separation (E5.4 cm À 1 at 1.6 K and 77 K [17][18][19]) between R 1 and R 2 lines in LaAlO 3 :Cr 3 þ being much smaller than that (E 24.1 cm À 1 at 77 K [19]) in LaGaO 3 : Cr 3 þ , the thermal shifts of two components R 1 and R 2 lines for LaAlO 3 :Cr 3 þ have not been reported until now, the R line can therefore be regarded as the average value of R 1 and R 2 lines).…”

“…with the Debye temperatures T D E375 and 400 K for LaAlO 3 :Cr 3 þ and LaGaO 3 :Cr 3 þ , respectively; and the electron-phonon coupling parameters α E 175, 215 and 260 cm À 1 for the R line of LaAlO 3 :Cr 3 þ , the R 1 and R 2 lines of LaGaO 3 :Cr 3 þ , respectively [19,20]. In their explanations [19,20], only the vibrational contribution due to electron-phonon interaction to thermal shifts is considered, while the static contribution due to thermal expansion of lattice is neglected because they assumed that the static contributions in these systems are very small.…”

“…In their explanations [19,20], only the vibrational contribution due to electron-phonon interaction to thermal shifts is considered, while the static contribution due to thermal expansion of lattice is neglected because they assumed that the static contributions in these systems are very small. No reasons for this assumption were given in their papers [19,20].…”