Low-temperature dielectric behavior of disordered and ordered langasite family single crystals LGS, LGT, SNGS and STGS

Abstract Dielectric measurements of disordered La 3 Ga 5 SiO 14 (LGS), La 3 Ga 5,5 Ta 0,5 O 14 (LGT) and ordered Sr 3 NbGa 3 Si 2 O 14 (SNGS), Sr 3 TaGa 3 Si 2 O 14 (STGS) single crystals of the langasite family performed at frequencies from 10 Hz to 1 MHz at temperatures between 4.2 and 300 K are reported. Temperature dependences of dielectric permittivity e 33 and e 11 are obtained. It is shown that e 33 in LGS and LGT exhibits incipient ferroelectric-like behavior. SNGS and STGS demonstrate ordinary dielectric temperature dependences as dielectric permittivity decreases down to helium temperatures.