Effect of pressure and magnetic field on the phase transitions in lanthanum-deficient manganites

Abstract

We report on the pressure, field and temperature dependencies of magnetization and resistance in manganites of (La1-xCax)1-yMn1+y O3 type. The M(T) dependencies is established to exhibit the following peculiarities: the first is connected with the paramagnet (PM)-ferromagnet (FM) transition at 267 K; the peak of M(T) dependence eat 263K is presumable due to an existence of AFM clusters; an anomaly in magnetization is connected with the FM-canted phase transition at 42K and the large irreversibility in the field-cooled and zero field- cooled magnetization. As field is increased above 200 Oe, the sign of the M(T) anomaly changes, namely, the M(T) magnetization increases with increasing field at 42K. The character of M(T) dependencies does not change under pressure. However, both the Curie temperature, Tc, and the resistance peak corresponding to metal-insulator transition shift in the direction of high temperatures with increasing pressure. A pressure stabilizes the ferromagnetic metallic phase. The temperature of the FM-canting phase transition does not change under pressure. The magneto resistance effect increase by 15 percent under pressure of 12.6 kbar.