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Hall resistivity and longitudinal magnetoresistance measurements were performed on epitaxial La0.67Ca0.33MnO3-delta thin films. The results revealed that the carrier is holelike and that the carrier density was a function of both temperature and magnetic field. The findings further showed that the carrier density is approximately 0.004 per unit cell in a field of 0.5 T and at 290 K.

The ferromagnetic transition temperatures have been measured on two bathes of perovskite manganese oxides such as (La1- x R x )2/3Ca1/3MnO3(R=Ce, Pr, Nd, etc.) and La2/3(Ca1- y Cd y )1/3MnO3. It is found that the (La1- x R x )2/3Ca1/3MnO3 samples have obviously different Curie temperature T C although their (rA) (the average A-site cation radius) are almost identical, and the T C in the system of (La1- x R x )2/3Ca1/3MnO3(R=Ce, Pr, Nd, etc.) and La2/3(Ca1- y Cd y )1/3MnO3. It is found that the (La1- x R x )2/3Ca1/3MnO3 compounds increases with increasing y although (rA) decreases slightly. It is suggested that the Curie temperature should be influenced by the average local A-site magnetic moment in the ferromagnetic perovskite manganite system. [ABSTRACT FROM AUTHOR]

Epitaxial La2/3Ca1/3MnO3 thin films were prepared on NdGaO3(1lO) substrates by d.c. magnetron sputtering method. The measurements of magnetoresistance ρ( H) upon magnetic field at different temperatures were carried out in the field range of 0–8 T. It is found that ρ( H) obeys the following relations: when the temperature (T) is higher than the Curie temperature $$T_C , \rho (H) = \frac{1}{{\alpha (T) + \beta (T)H^2 }}$$ below $$T_C , \rho (H) = \rho _0 (T) + \frac{1}{{A(T) + B(T)exp(H/C(T))}}$$ and $$\rho (H) = \frac{1}{{\sigma (T) + \gamma (T)H}}$$ when T is far Wow T c. It is suS8ested that the negative magnetoresistive effect is mainly due to enhancement of the magnetoconductance. [ABSTRACT FROM AUTHOR]