| In the past half a century’s development, great progress has been achieved in Condensed matter physics, which has been the most important branch of physics. Among them, Strongly-Correlated electrons system physics remains to be a puzzling problem which needs solving. In the practical application of the drug in the treatment of trees diseases material coated on the magnetic material, guide material control carrying drugs and magnetic field of the magnetic material, gathered in pathological changes of trees. In order to enhance the therapeutic effect of disease to trees, and reduce the drug to the pathological changes of trees without side effects.Due to the Strongly-Correlated electrons system, perovskite manganites attract more and more attention in physicists. Since the 1980s, the specific study of perovskite manganites created quite a stir. Various types of models have been set by researchers, such as double exchange models and polaron models to analysis the complex effects among them. In the meantime, considering the complex inner structure, charge, spin orbital, crystal latticeand the interactions of Strongly-Correlated electrons system, some new phenomenon still remains to be explained. In this way, it is essential to continue the deep study in perovskite manganites.In this dissertation, Nd0.5Ca0.5Mn1-xAlxO3 (x= 0,0.025,0.05,0.075,0.10,0.15, 0.20,0.30) has been prepared using solid phase reaction. Serious of single phase samples and poly crystal samples have been chosen, whose resultant temperature can be as high as 1300 ℃ for twenty-four hours. Through X-ray diffraction, the results of samples have been represented. With the help of Physical Property Measurement System, the magnetization, magnetic hysteresis loop has been measured.After analyzing diffractions and patterns of XRD, it turns out that all of the samples have single-phase orthorhombic structures, whose space groups are pnma and the maximum diffraction peak are about 33.38 °. With the doping of Aluminium, no obvious changes in the location of the diffraction peak can be detected.On the light of M-T curves of the series of samples, we can draw a conclusion that the doping of Aluminium has an obvious influence on the magnetization of the samples. The temperature of charge ordering in Ndo.5Ca0.5MnO3 is 249 K. When x turns to be equal or greater than 0.025, a sharp peak of ZFC can be observed at the temperature of nearly 40 K, which means the freezing temperature. Under the temperature of 2 K, the magnetization of samples’FC curve strengthen with the doped increasing in amount, which means that the doping of Aluminium may have an inhibiting effect the order of anti-ferromagnetic, and in this way samples’ ferromagnetism can be strengthened.The isothermal magnetic hysteresis loops of all the samples are measured at 2 K.It can be seen that no magnetization step is observed for the undoped sample and the saturation is not reached at applied field of 9 T.This is attributed to the stronger charge ordered(CO) state of Nd0.5Ca0.5MnO3.x= 0.05 sample show magnetization step,because of the system is phase separation state at low temperatures,the antiferromagnetic(AFM) phase to a ferromagnetc(FM) phase under the external magnetic field.The interfacial strain can be destroyed drastically when the field is up to the critical field Hc,the ferromagnetic fraction increases dramatically,resulting in the existernce of magnetization step. |
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