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中文摘要：
通过溶胶-凝胶法，合成了稀土Dy^3＋掺杂的Fe3O4样品，研究了掺杂对电磁性质的影响。通过X射线衍射分析发现，由于离子半径的不匹配，Fe3O4中稀土离子的高浓度掺杂不能实现，仅有极少量的稀土离子取代了Fe3O4中的Fe^3＋。通过振动样品磁强计对磁性质进行了表征，掺杂引起样品饱和磁化强度发生变化，这可能是因为Dy^3＋取代引起的磁化强度增加和杂相引起的磁化强度降低共同作用的结果。四电极法研究隧道磁阻发现，磁阻与掺杂量的关系表现出降低-升高-降低的特殊变化规律。这主要是由于掺杂Fe3O4自旋极化率降低导致隧穿磁阻下降，同时，掺杂Fe3O4在隧穿颗粒体系中实现了第二相即绝缘相的同步合成，第二相的出现有利于隧穿磁阻的增加。
英文摘要：
The Dy^3＋-doped Fe3O4 samples were synthesized by sol-gel method, and the effects of dopant on the electrical and magnetic properties were investigated. According to XRD analysis, the high concentration doping of dysprosium ions in Fe3O4 can not be obtained due to the difference of ionic radius, and Fe^3＋ ions are replaced by only a small amount of dysprosium ions. The magnetic property was characterized by VSM. The substitution results in the change of saturation magnetization, which may be due to the complex effects of increasing magnetization resulted from Dy^3＋ substitution and decreasing magnetization resulted from the impurity. The electrical property was characterized by four-probe method. With the increasing doped content, magnetoresistance also increases, then decreases, and increases again. The spin-polarization of doped samples is lower than that of Fe3O4. Lower spln-polarization results in lower tunneling magnetoresistance. Fortunately, barrier was obtained by the second phase at the same time when sample was synthesized. The increase of appropriate barrier height leads to the change of tunneling magnetoresistance.
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