Internal Bias Field of Sarcosine-Doped Triglycine Sulfate Crystal

Single crystals of ferroelectric triglycine sulfate (TGS) have been grown from aqueous solution containing 10 mol% of sarcosine. The crystal, referred to as SarTGS, shows a quite different habit from undoped TGS. The concentration of sarcosine incorporated in the crystal is, at most, 1/500 of the solution concentration. Although sarcosine is not chiral, an internal bias field E b of 40-140 kV/m is produced. The direction and intensity of E b, as well as the domain structure, vary according to the crystal growth sector. The directions of E b in matching sectors in both b sides of the seed crystal are opposite to each other. In the sectors where the growing surface is parallel to the b-axis, no bias field is produced. The cause of such a feature of E b in the SarTGS crystal is discussed in terms of symmetry considerations.