M. Drulis

Antiferromagnetic ordering in terbium dihydride. Low temperature heat capacity studies

Abstract The specific heat of terbium dihydride, TbH 2.01 , was measured in the temperature range from 4–200 K. An extremely sharp λ-type specific heat anomaly due to an antiferromagnetic transition has been found at T N = 16.06 ± 0.01 K.

Low temperature specific heat of Na0.5Bi0.5TiO3 single crystals

The heat capacity Cexpt(T) of Na0.5Bi0.5TiO3 single crystals for the temperature range 5 to 186 K is reported for the first time. The broad maximum on CexptT—3 plot in the temperature range 10 K 〈 T 〈 25 K and rapid rise in this plot with decreasing temperature below ≈10 K was observed. This maximum can be represented by a single Einstein mode (51 cm—1), and the fitted Debye temperature (180 K) is close to the value obtained from pyroelectric measurement (185 K). The obtained data display non-Debye features and suggest glass-like properties of NBT at low temperatures. Die spezifische Warme Cexpt(T) fur Na0.5Bi0.5TiO3-Kristalle im Temperaturbereich von 5 bis 186 K wird erstmals vorgestellt. Eine Anomalie im Diagramm CexptT—3 wurde im Bereich 10 K 〈 T〈 25 K beobachtet. Ein groser Anstieg von CexptT—3 mit geringer werdender Temperatur unter ≈10 K wurde bemerkt. Diese Anomalie kann durch ein “Einstein single mode” beschrieben werden. Die Debyetemperatur (180 K) entspricht dem Wert aus pyroelektrischen Untersuchungen (185 K). Die erhaltenen Ergebnisse zeigen eine Debyeverhaltung und weisen auf glasahnliche Eigenschaften bei tiefen Temperaturen hin.

Low temperature specific heats of samarium trihydride. Second-order phase and crystal field splitting effects

Abstract The specific heat of samarium hydride, SmH2.84, was measured in the temperature range from 2–244 K. A λ-type specific heat anomaly most probably due to a magnetic transition was found at TN = 25.8 ± 0.5 K. Schotty specific heat anomalies due to crystal field splitting effects were found and analysed.

Low‐Temperature Specific Heat of (Na0.5Bi0.5)0.86Ba0.14TiO3 Single Crystal

The heat capacity C p (T) (at 5 to 280 K) of (Na 0.5 Bi 0.5 ) 0.86 Ba 0.14 TiO 3 single crystal is presented for the first time. The obtained data are fitted and discussed with expressions, which contain linear, Debye and Einstein contributions. The fitted parameters (Debye temperature, Einstein temperature) are close to those reported for the Raman scattering measurements. The results are compared with data for the undoped ferroelectric Na 0.5 Bi 0.5 TiO 3 . A glass-like behaviour of (Na 0.5 Bi 0.5 ) 0.86 Ba 0.14 TiO 3 at low temperatures, similarly as for pure Na 0.5 Bi 0.5 TiO 3 , has been revealed.