缺氧YBCO多晶陶瓷的磁电耦合与磁电阻效应

Magnetoelectric coupling and magnetoresistance in oxygen-deficient YBCO ceramics

将高温超导陶瓷YBa2Cu3O6+x经过真空热处理得到氧含量x=0.13的缺氧陶瓷样品,利用HP4294A精密阻抗分析仪测量了样品介电常数温谱图,在温度为410K附近发现了介电异常现象,认为是由反铁磁相变感应铁电相变引起的。铁电测量表明缺氧YBCO多晶陶瓷在室温下有一定的铁电性。在零磁场和外加磁场条件下,采用标准四引线法分别测量了样品电阻率随温度的变化关系,发现温度低于400K时样品的磁电阻MR约为60%且基本不随温度变化,在反铁磁相变温度410K附近出现异常,认为是由于样品大量本征载流子产生并且外加磁场对顺磁区域影响较小所致。缺氧YBCO(x=0.13)陶瓷样品的磁电耦合特性,显示出它可能成为一种新的室温多铁材料从而在传感、控制和信息储存等方面发挥重要作用。

Polycrystalline YBa2Cu3O6.13 ceramics were prepared by solid state reaction. Temperature dependence of dielectric constant of this oxygen-deficient YBCO sample was measured in the frequency range from 100Hz to 1MHz with a HP4294A precision impedance analyzer. An abnormal dielectric behavior was observed in the vicinity of antiferromagnetic phase transition, which is attributed to the induced ferroelectric transition. In addition, room temperature ferroelectric hysteresis loops of the YBCO ceramics were obtained using a RT 6000 ferroelectric analyzer. The results indicate the existence of ferroelectricity in the sample at room temperature. Temperature dependence of dc resistivity of the sample in zero field and in the presence of a 0.4T magnetic field was measured with standard four lead method. It has been found that applying magnetic field reduces the resistivity of the sample and the magnetoresistance MR of YBCO ceramics reaches a value of 60% below the antiferromagnetic phase transition. A sharp drop in magnetoresistance near the magnetic phase transition suggests a strong magnetoelectric coupling which could potentially have important ramifications in devices such as sensors and information storage. The oxygen deficient YBCO ceramics could be a promising candidate for room temperature multiferrocs.