Co掺杂的ZnO稀磁半导体块体的退火热处理研究

High temperature annealing treatment on Co doped ZnO bulks

采用固相反应法制备了Zn0.95Co0.05O块体样品,并对其进行了不同方式的退火处理.实验表明在锌气氛中500℃退火的样品表现出铁磁性,而在真空中退火的样品却没有磁性,进一步,在锌气氛中1100℃退火的样品虽然表现出铁磁性,但其铁磁性来源于样品在锌气氛中1100℃退火过程中产生了1%左右的Co金属团簇杂质相.另外,在低温时所有样品都表现出较大的正磁电阻,认为正磁电阻效应是由于s-d电子交换相互作用引起的自旋劈裂造成的,而高场时出现的负磁电阻效应则可能归因于磁场导致的束缚磁极化子的破损和自旋散射的抑制.

Zn0.95Co0.05O Bulk samples were synthesized by solid state reaction method and annealed by different processes. The Zn treated samples show ferromagnetism, whereas the vacuum annealed samples do not show ferromagnetism. The XRD patterns show that there is Co impurity phase in the sample after Zn treatment at 1100℃ ,which is the reason of the ferromagnetism observed. At low temperature, both the positive and negative magnetoresistance （MR） effect can be observed for all the samples. We conclude that the s-d exchange-interaction-induced spin-splitting gives rise to positive MR, while the formation of bound magnetic polarons and the magnetic field suppressed spin-disorder scattering are responsible for the negative MR behavior under high field.