| The crystal structure of manganese oxide is similar to the crystal structure of CaTiO3, So it is called perovskite manganite。 The perovskite manganese oxide materials showed a100%spin polarization and the colossal magnetoresistance (CMR), so the perovskite manganese materials not only have significant potential application and contain many physics such as the double exchange interaction, the jahn-teller effect, the magnetic phase transition along with the electrical conductivity changes, the spin ordering, lattice effects, charge orderly, orbital ordering and their mutual coupling。In this thesis, we have mainly studied the influence of A-doped and B-doped to the magnetoimpedance of La0.67Ca0.33MnO3manganese materials。 We also studied the insulation coating technology of soft magnetic composite。In the course of studying, we found a material with both the function of insulation and the function of lubrication。 The abstracts of our results as follows:1.X-ray diffraction analysis the nanocrystalline’s materials structure of the sol-gel Lao.67Cao.33Mn1-xCoxO3(X=0.01,0.03,0.05,0.07), Lao.67Cao.33Mn1-xZnxO3(X=0.01,0.03,0.05,0.07), La0.6Ba0.4MnO3, which indicated these structure are single perovskite structure and it showing the structure of perovskite is very steady。We take four-point method by the HP4294A magneto-impedance analyzer to measure the magneto-impedance of materials。2.Firs we choosed the magnetic element Co as B doping impurities。The sol-gel La0.67Ca0.33Mn1-xCoxO3(X=0.01,0.03,0.05,0.07) nanocrystalline materials with an external H=1000Oe found that the maximum DC magnetoresistance effect value in the X=0.03was-23.4%,it showed good magnetoresistance effect。However, when the H=1000Oe, the sol-gel La0.67Ca0.33Mn1-xCoxO3(X=0.01,0.03,0.05,0.07) at X=0.03and AC frequency f=10Mhz achieved the maximum nanocrystalline materialsAC magnetoresistance effect value of-36.32%, while the magneto-impedance effect of the material also reached a maximum value of-28.74。we found that the Co-doping when X=0.03have the largest effect on the magnetoimpedance of material and the magnetoimpedance effect have selectivity to AC frequency。3.The fourth chapter of this paper we have chosen a non-magnetic element Zn doping as B in the same experiment conditions to observe the non-magnetic element Zn on the magnetoimpedance effect of the sample material。The maximum DC magnetoresistance effect of the sol-gel Lao.67Cao.33Mn1-xZnxO3(X=0.01,0.03,0.05,0.07) with an external H=100oe are11.56%,-24.69%,-16.67%,-12.11%. we can found that the X=0.03have the largest DC magnetoresistance effect value。The maximum AC magnetoresistance effect and the largest AC magnetoi also appeared at the doping concentration X=0.03with the external magnetic field H=1000Oeo However the AC magnetoresistance effect and the AC magnetoimpedance effect caused by the magnetic element Co are different to the non-magnetic element Zn。The maximum AC magnetoresistance effect of-35.64%appeared at low-frequency f=2Mhz and the maximum AC magnetoimpedance effect of-25.80appeared at low-frequency f=1Mhz。We can observe that the biggest effect on the magnetoimpedance caused by the magnetic element Co appeared at high AC frequency。However the largest effect on the magnetoimpedance caused by the non-magnetic element Zn appeared at low AC frequency。4.The DC magnetoresistance of sol-gel La0.6Ba0.4Mn04nanocrystalline at room temperature under600Oe external magnetic field is very small。The magnetoresistance effect value is only-1.97%。The maximum AC magnetoresistance is-41.92%with external H=600Oe and the maximum AC magnetoimpedance value is-28.46%。and it much higher than the DC magnetoresistance effect value。5we also studied the coated insulation of soft magnetic composite。We used a comparison of the phosphate coating and nano-scale inorganic oxide ZnO coating。 We found that the ZnO coating with both the function of insulation and the function of lubrication... |
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