Structure And Physical Properties Of Perovskite Manganites Nd_0.9Zr_0.1MnO₃ And (La_1-xPr_x)_0.55Ca_0.45MnO₃(x=0-1)

Structure and physical properties of electron-doped manganite Nd0.9Zr0.1MnO3 and hole-doped manganite (La1-xPrx)0.55Ca0.45MnO3 (x = 0, 0.2, 0.4…1) have been investigated systemically.For Nd0.9Zr0.1MnO3, the x-ray diffraction investigation shows that the compound is in single phase with a few of neglectable impurities. Crystal structure of the compound can be indexed by an orthorhombic lattice with Pbnm space group. The x-ray photoemission spectroscopy investigation shows that the Mn cations are in the divalent and trivalent states. M-T curves are recorded under zero-field-cooled and field-cooled mode, and the magnetization reversal phenomena are observed both in the two mode curves. The Mn2+/Mn3+ and Mn3+/Mn3+ two sublattices theory is employed to explain the experimental results. A physical picture related to the magnetization of the two set of sublattices is proposed to depict the temperature dependence of the magnetization variation of the sample. The specific heat curve shows three peaks, providing a strong support on this physical picture. The electrical transport properties exhibit an insulator behavior and the colossal magnetoresistance effect is not prominent in this compound.For (La1-xPrx)0.55Ca0.45MnO3 (x = 0-1), the x-ray diffraction investigation shows that all the compounds are in single phase with the orthorhombic lattice and Pnma space group. With increasing the Pr doping level, both the lattice parameter and the unit cell volume reduce, but the bond lengths and the bond angles of the Mn-O bond don't vary monotonically. In the M-T curves, with increasing x, the ferromagnetic coupling is weakened, and the charge ordering states are strengthened. Meantime, the charge ordering temperature rises, while the Curie temperature drops when increasing x. In the M-H curves, the metamagnetic transitions can be observed for all the x≥0.4 compounds. With increasing x, the critical magnetic field inducing the transition increases, and the hysteresis is more obvious. The T-H phases diagrams of the x = 0.4-1 samples are drawn based on the M-T curves and the M-H curves, from which the phase separation areas can be observed, the transition from the charge ordering to ferromagnetic state shows the reentrant characteristic. The electron spin resonance investigation indicates that two phases coexist in the 195 K-150 K regions, which is...