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Intrinsic and spatially nonuniform ferromagnetism in Co-doped ZnO films
Physical Review B ( IF 3.7 ) Pub Date : 2017-09-18 00:00:00 , DOI: 10.1103/physrevb.96.104423
L. T. Tseng , A. Suter , Y. R. Wang , F. X. Xiang , P. Bian , X. Ding , A. Tseng , H. L. Hu , H. M. Fan , R. K. Zheng , X. L. Wang , Z. Salman , T. Prokscha , K. Suzuki , R. Liu , S. Li , E. Morenzoni , J. B. Yi

Co doped ZnO films have been deposited by a laser-molecular beam epitaxy system. X-ray diffraction and UV spectra analysis show that Co effectively substitutes the Zn site. Transmission electron microscopy (TEM) and secondary ion mass spectroscopy analysis indicate that there are no clusters. Co dopants are uniformly distributed in ZnO film. Ferromagnetic ordering is observed in all samples deposited under an oxygen partial pressure, PO2=103, 105, and 107 torr, respectively. However, the magnetization of PO2=103 and 105 is very small at room temperature. At low temperature, the ferromagnetic ordering is enhanced. Muon spin relaxation (μSR) measurements confirm the ferromagnetism in all samples, and the results are consistent with magnetization measurements. From μSR and TEM analysis, the film deposited under PO2=107 torr shows intrinsic ferromagnetism. However, the volume fraction of the ferromagnetism phase is approximately 70%, suggesting that the ferromagnetism is not carrier mediated. Resistivity versus temperature measurements indicate Efros variable range hopping dominates the conductivity. From the above results, we can confirm that a bound magnetic polaron is the origin of the ferromagnetism.

中文翻译:

共掺杂ZnO薄膜中的固有和空间上不均匀的铁磁性

共掺杂的ZnO薄膜已通过激光分子束外延系统沉积。X射线衍射和UV光谱分析表明,Co有效地替代了Zn位点。透射电子显微镜(TEM)和二次离子质谱分析表明没有簇。Co掺杂剂均匀分布在ZnO薄膜中。在氧气分压下沉积的所有样品中均观察到铁磁有序,采购订单2个=10-3 10-5, 和 10-7分别为torr。但是,磁化强度采购订单2个=10-310-5在室温下很小。在低温下,铁磁有序性得到增强。介子自旋弛豫(μSR)测量确认了所有样品中的铁磁性,并且结果与磁化强度测量结果一致。从μSR 和TEM分析,将薄膜沉积在 采购订单2个=10-7torr显示出内在的铁磁性。但是,铁磁性相的体积分数约为70%,这表明铁磁性不是载体介导的。电阻率对温度的测量结果表明,Efros可变范围跳变在电导率中占主导地位。从以上结果,我们可以确定束缚的磁极化子是铁磁性的起源。
更新日期:2017-09-19
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