Crystal-field analysis for RE3+ ions in laser materials: III. Energy levels for Nd3+ and Er3+ ions in LaAlO3, YAlO3, and LaGaO3 single crystals – Combined approach to low symmetry crystal field parameters

Display Omitted Highlights: ► CF analysis of energy levels for Nd3+ and Er3+ ions in ABO3 crystals is presented. ► Combined ADS/SPM strategy is employed. ► Its usefulness for successful analysis of low-symmetry systems is proved. ► Structural relationships between different ion–host systems are emphasized. - Abstract: Crystal field (CF) analysis of energy levels for Nd3+ and Er3+ ions in LaAlO3, YAlO3, and LaGaO3 single crystals is presented. It is shown that a combined approach comprising the ascent/descent in symmetry (ADS) method combined with superposition model (SPM) analysis can be successfully used for analysis of low-symmetry systems. The present ADS/SPM approach is less labor and time consuming as compared, e.g., with Monte-Carlo method and it also allows maintaining the relationship between the crystallographic axis system and the nominal axis systems of fitted CFP sets. For orthogallates and orthoaluminates the actual Cs symmetry, resulting from distortion of perovskite structure, may be successfully approximated for both systems by the ADS chain C4v ↔ C3 (D3) ↔ Cs or C3 (D3) ↔ Cs symmetry. The possibility of using of approximated symmetries for orthogallates or orthoaluminates can be useful for interpretation of energy levels for this family of compounds of technological importance, particularly in the case when the number of available experimental energy levels is insufficient for full Cs parameterization. The novel aspect of the combined ADS/SPM approach is that possible higher symmetry approximations employing also the axis systems oriented differently than for the actual symmetry are searched for, taking advantages of the transformation properties of CF parameters sets.