Abstract
Attenuation and phase velocity of ultrasound have been measured in strontium fluoride single crystal doped with chromium in the temperature range of 4 – 185 K at 56 -162 MHz. Anomalies have been found for all the normal modes corresponding to the non-vanishing elastic moduli of a cubic crystal. Interpretation of the observed anomalies has been done in the framework of relaxation in the system of Jahn-Teller (JT) complexes CrF8 subject to full T2g ⊗(eg + t2g) JT problem. Relaxation time has been calculated from the experimental data on ultrasonic attenuation and adiabatic and isothermal contributions of the impurity subsystem to the total elastic moduli have been obtained.
Highlights
Recent study of II-VI and III-V crystals doped with 3d metals with degenerate orbital states proved the efficiency of ultrasonic experiment for investigating properties of the Jahn-Teller (JT) centers [1]
Published under licence by IOP Publishing Ltd resonance methods, ultrasonic experiments deal with relaxation in the system of the JT impurities which occurs among equivalent JT distortions
The anomalies were interpreted as relaxation between equivalent JT distortions of the CrF8 complexes
Summary
Recent study of II-VI and III-V crystals doped with 3d metals with degenerate orbital states proved the efficiency of ultrasonic experiment for investigating properties of the Jahn-Teller (JT) centers [1] (see, e.g., [2,3,4,5] and references therein) It provides independent and sometime unique information about electronic structure, dynamics and local symmetry of point defects in addition to obtained by traditional methods such as electron spin resonance, pulse techniques using electron spin echo, electron spin envelope modulation spectroscopy [6,7,8,9,10], and other methods [11,12,13,14]. We present new results on temperature dependences of the elastic moduli, prove the relaxation nature of the anomalies found at low temperatures and verify the choice of background attenuation using the method suggested above
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