Volume 101A, number 2 PHYSICS LETTERS 12 March 1984 CRITICAL TRANSMISSION OF BETA PARTICLES THROUGH THICK FERROELECTRIC TARGETS AT THE CURIE TEMPERATURE M.T. LAGARE Department of Physics, Gulbarga University, Gulbarga 585 105, India and N. UMAKANTHA Department of Physics, Karnatak University, Dharwad 580 003, India Received 11 February 1983 Revised manuscript received 8 November 1983 The intensity of beta particles transmitted through thick targets of barium titanate and triglycene sulphate shows an anomalous decrease at the Curie temperature indicating a new mode of energy loss of electrons in ferroelectrics at the Curie temperature. Recently [1] we have reported that the energy loss of 620 and 942 keV electrons in barium titanate (BT), as well as that of 942 keV electrons in triglycene sul- phate (TGS), is anomalously high at the Curie tempera- ture, indicating that the dynamics of short-range or- der in the ferroelectric state of the medium at the Curie temperature plays a role in the energy loss of electrons. Though transmission of beta particles through a thick target is complicated by multiple elastic and inelastic scattering, any anomalous in- crease in the stopping power of a ferroelectric me- dium at the Curie temperature should be reflected in the intensity of transmitted beta particles and offer a method of detecting its presence even at higher elec- tron energies than are provided by the available inter- nal conversion electron sources. With this in view we have, in a standard good geometry G.M. setup shown schematically in fig. 1, measured the intensity of beta particles from Sr-Y-90 (end-point energy 2.284 MeV) and Ce-Pa-144 (end-point energy 2.996 MeV) sources transmitted through thick targets of BT and TGS as a function of target temperature. Our results show an anomalous low transmission in the neighbourhood of the Curie temperature in the case of both the targets. Large single crystals of TGS were grown from 0.375-9601/84/$ 03.00 © Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division) F ~ H F Fig. 1. Schematic diagram of the G.M. setup. S source, C aluminum collimators, GM G.M. detector, H. planchet, T target, F aluminum foils, A additional collimators, P perspex and L lead. solution and targets were cut from these and poUshed to desired thickness. Polycrystalfine targets of TGS and BT were prepared by pressing finely ground powder under a pressure of 100 kg cm -2. The target was placed between two thick aluminum collimators which were heated electrically to vary the tempera- 103