磁铁矿薄膜自发极化的热释电探测
Pyroelectric detection of spontaneous polarization in magnetite thin films
摘要：
用动态和静态热释电测量方法研究了Fe $_3$ O $_4$薄膜的自发极化。在Nb：SrTiO $_3$（001）基片上生长的Fe $_3$ O $_4$薄膜的磁性和介电性能与体相晶体一致。在120 K时观察到了著名的金属-绝缘体（Verwey）转变。Fe $_3$ O $_4$薄膜在低于Verwey温度时出现热释电响应，表明Fe $_3$ O $_4$在电荷有序转变温度时出现自发极化.极性态特征与Fe $^{2+}$和Fe $^{3+}$离子共享八面体$B$位点的键中心和位点中心电荷有序一致。Fe $_3$ O $_4$薄膜的热释电响应依赖于介电常数。对Pd/Fe $_3$ O $_4$ /Nb：SrTiO $_3$结的准静态热释电测量表明，磁铁矿在60 K时具有很大的热释电系数，为735 nC/cm $^{2}$ K。
英文摘要：
We have investigated the spontaneous polarization in Fe$_3$O$_4$ thin films by using dynamic and static pyroelectric measurements. The magnetic and dielectric behavior of Fe$_3$O$_4$ thin films grown on Nb:SrTiO$_3$(001) substrates was consistent with bulk crystals. The well-known metal-insulator (Verwey) transition was observed at 120 K. The appearance of a pyroelectric response in the Fe$_3$O$_4$ thin films just below the Verwey temperature shows that spontaneous polarization appeared in Fe$_3$O$_4$ at the charge ordering transition temperature. The polar state characteristics are consistent with bond- and site- centered charge ordering of Fe$^{2+}$ and Fe$^{3+}$ ions sharing the octahedral $B$ sites. The pyroelectric response in Fe$_3$O$_4$ thin films was dependent on the dielectric constant. Quasi-static pyroelectric measurement of Pd/Fe$_3$O$_4$/Nb:SrTiO$_3$ junctions showed that magnetite has a very large pyroelectric coefficient of 735 nC/cm$^{2}$K at 60 K.
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