EPR investigations of solid solutions of TSCC and TSCB doped with Mn²⁺

Abstract

Dedicated to Professor Hermann NEELS on the occasion of his 65th birthday EPR investigations of Mnz+-doped solid solutions of TSCC and TSCB were performed between 4.2 K and 300 K. The Curie temperature vs. molar fraction of bromide x is nonlinear, for z 2 0.75 no ferroelectric EPR-line splitting occurs. The relation between the line widths and the molar fraction of bromide is discussed by means of a simple statistical model.An festen Losungen von Mn2+-dotiertem TSCC und TSCB wurden zwischen 4,2 K und 300 K EPR-Untersuchungen durchgeftihrt. Die Abhiingigkeit der Curie-Temperatur vom molaren Bromidgehalt z ist nichtlinear, fur z 2 0,75 tritt keine der spontanen Polarisation proportionale EPR-Linien-Aufspaltung mehr auf. Die Beziehung zwischen der Linienbreite und dem molaren Bromidgehalt wird mit Hilfe eines einfachen statistischen Modells diskutiert.

Pressure and temperature dependence of dielectric properties of brominated trissarcosine calcium chloride

“…Although a ferroelectric phase transition in TSCB has not been observed in the temperature range 30 "C to -269 "C under atmospheric pressure (Navalgund andGupta 1975, Treeck andWindsch 1978), we could observe in this work that the ferroelectric phase transition in TSCB is caused by the application of pressure. Figure 4 shows the temperature dependence of E,, l/&, and P, of TSCB for different pressures.…”

“…The crystals were grown from an aqueous solution of calcium chloride and calcium bromide and sarcosine in stoichiometric proportions by the slow evaporation method at 30 "C (Makita 1965, Treeck andWindsch 1978). The molar fraction x of bromide in the mother solution varied between x = 0 and x = 1.0.…”

“…The molar fraction x of bromide in the mother solution varied between x = 0 and x = 1.0. The growth features of TSCCB are similar to those of TSCC, and are multi-twinned (Navalgund andGupta 1975, Treeck andWindsch 1978). Non-twinned parts were chosen by means of a polarising microscope (Sawada eta1 1977).…”

“…On the other hand, trissarcosine calcium bromide ((CH3NHCH*COOH)3 CaBr2, abbreviated TSCB) has been shown to be isostructural to TSCC (Navalgund and Gupta 1975). However, no ferroelectric transition in TSCB has been observed in the temperature range 30 "C to -269 "C at atmospheric pressure (Navalgund andGupta 1975, Treeck andWindsch 1978). It has been suggested from this fact that the profile of the potential in which the proton moves in the N-H-X bond (X = Cl, Br) is quite sensitive to the nature of the X atom, and the proton in the N-H-Cl bond may be playing an important role in the mechanism of ferroelectricity in TSCC (Navalgund andGupta 1975, Treeck andWindsch 1978).…”

“…It has been suggested from this fact that the profile of the potential in which the proton moves in the N-H-X bond (X = Cl, Br) is quite sensitive to the nature of the X atom, and the proton in the N-H-Cl bond may be playing an important role in the mechanism of ferroelectricity in TSCC (Navalgund andGupta 1975, Treeck andWindsch 1978). Moreover it has been reported that the EPR spectra of the brominated trissarcosine calcium chloride ((CH3NHCH2COOH)3CaC1~~l-x)(Br2)x, abbreviated TSCCB) for x S 0.6, split at the transition temperatures in the temperature range 30 "C to -269 "C and the transition temperature decreases rapidly with increasing x (Treeck and Windsch 1978). In this paper, the dielectric properties of TSCCB (x 6 1.0) are presented in order to confirm whether the transition is ferroelectric or not.…”