Magnetotransport Behavior and the Phase Diagram of Nd $_{1 - {\rm x}}$ Ca $_{\rm x}$ MnO<

In this work, the temperature dependent magnetization M(T) and the electrical resistivity rho (T) of Nd_1-xCa_xMnO₃ (x=0.1-0.5) are measured. From the M(T) curves, the ferromagnetic (FM) phase is observed for samples of x=0.1 and 0.2. However, the canted-antiferromagnetic (CAF) phase which coexists with the charge-ordering (CO) phase occurs at low temperature for samples x=0.3-0.5. By systematically changing the Ca concentration from x=0.1 to 0.5, a detailed phase diagram is established. Based on the result of magnetic field dependent rho (T), the magnetoresistance ratio is calculated, which shows a maximum in the x=0.4 sample. These results are helpful for improving the MR effect in these manganites.