Electric Field Effect on ¹⁴N NQR in Ferroelectric Thiourea Single Crystals

Abstract

The electric field effect on 14 N NQR in ferroelectric thiourea [SC(NH2)2] single crystals has been investigated at 77 K up to a field of 10 kV/cm. The measured Stark shifts are, in units of kHz • cm/ kV, dvj h /d£+ = 0.87±0.10, dvx + /d£_ = 1.17±0.20, dv2 + /d£+ = 0.80±0.10, and dv2 + /d£_ = 0.90 ±0.15. These values are on the order of 10 2 times those found in other ferroelectric crystals such as sodium nitrite (NaN02). The remarkable difference between these two Stark shifts is discussed by taking into account the polarizability and the local electric field at the 14 N sites in these crystals.