Memory effect in ferroelectric-semiconductor with incommensurate phase TlGaSe2

10.1007/s11451-008-1020-5

“…1a, the ε(T) curve has a number of anomalies in the form of maxima related to the PTs into the INC phase at T i ~ 119 K and into the ferroelectric C phase at T c~ 107 K, and ε(T) of TlGaSe 2 -I is maximal at the INC-phase PT temperature. Our measurements indicate that the ε(T) dependence in the high-temperature paraelectric phase is well approximated by the Curie-Weiss law and that the Curie constant (C ~ 10 4 K -1 ) agrees satisfactorily with the data in [37,38,[41][42][43][44]. Note that the ε(T) temperature dependence of a sample of this technological quality differs slightly from the reported ε(T) dependences and the temperature dependence of the dielectric loss tangent tanδ of layered TlGaSe 2 crystals chosen from different technological batches [37,38,[41][42][43][44] in a weak anomaly near 110 K. (See the inset to Fig.…”

“…Unfortunately, our experimental possibilities are such that we can identify this difference only upon very slow temperature scanning of a sample. Under these experimental conditions, it is inconvenient to choose cooling conditions to study the ME of the INC phase in TlGaSe 2 , since, first, the effect can be "lost" because of the DDW relaxation time and, second, long-term residence in the temperature range of the INC phase (especially near T c from the side of the INC phase) can cause an additional long-lived metastable state, i.e., the superposition of spontaneous modulation and the modulation induced by annealing at T 0 [38].…”

“…Note also that TlGaSe 2 crystals are characterized by a deviation from a stoichiometric composition and the formation of many polytypes [34][35][36]. The memory effect (ME) of the INC phase in TlGaSe 2 was studied in detail in [37,38], where ε ( T ) curves were measured and analyzed. This effect consists in the following.…”

“…(3) Another anomaly appears in the ε ( T ) curve in the vicinity of T c when this curve is measured upon annealing at T 0 [38].…”

Thermal history and dielectric behavior in the incommensurate phase of TlGaSe2

“…These phenomena are usually attributed to defect-induced pinning of the incommensurate structure what leads to dependence of the various physical properties on sample prehistory and thermal cycles. The presence of these effects in TlGaSe 2 is noticed recently in the results of the dielectric constant measurements [11][12][13].…”