Temperature dependence of the spontaneous polarization, acoustic and strain anomalies in strontium barium niobate crystals of different chemical compositions probed by the second harmonic generation technique

In SrxBa1-xNb2O6 crystals (x = 0.33, 0.5, 0.61, and 0.75), temperature dependences of spontaneous polarization, strain, elastic modules, and second harmonic generation (SHG) signal are compared. It is revealed that SHG describes the temperature dependences of dipole moments in polar nanoregions in paraelectric phase. In the vicinity of the phase transition in paraelectric phase, SHG reflects the temperature behavior of relatively large and long-lived polar asymmetric regions as indicated by the presence of the intermediate temperature range on the temperature dependence of this nonlinear response.