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The specific heat of Na,,.&,TiO, crystal in the temperature range 300-650 K and the changes of spontaneous polarization of Na&h;TiO, ceramic in the temperature range 4.2-90 K were measured. The calorimetric measurements showed that the anomaly of specific heat exists in the temperature range where the phase transition rate from the rhomhedral phase to the tetragonal phase is utmost. From lowtemperature pyroeleceic effect a phonon wave number equal to 128 cm-' was found to have the main share in the temperature changes of spontaneous polarization.

MottoThe first address of Satan to the human race began most modestly with the word: why? Adam Mickiewicz (1798-1855)The resistance, magnetoresistance and magnetization measurements have been performed in the temperature range of 4.2-300 K and in the external magnetic inductions up to 14 T for the Sm 1Àx Sr x MnO 3 (x ¼ 0.33, 0.45) and RE 0.55 Sr 0.45 MnO 3 (RE 0.55 ¼ Eu 0.397 Nd 0.153 , Tb 0.25 Nd 0.30 ) manganites. In these samples the metal-semiconductor phase transitions as well as two kinds of the magnetic phase transitions the ferromagnetic-paramagnetic and metamagnetic (both spin-flip and spin-flop) have been observed. It was found that correlations between the magnetic and electrical phase transitions appear at high values of the external magnetic inductions. These correlations consist, simultaneously, of the large negative magnetoresistance and metamagnetic phase transitions. The existence and reconstruction of the ferromagnetic and antiferromagnetic clusters under the influence of the external magnetic induction is considered as a driving force of those correlations.

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