Tunneling magnetoresistance induced by controllable formation of Co filaments in resistive switching Co/ZnO/Fe structures

Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering (NIMTE), Chinese Academy of Sciences (CAS) - Ningbo 315201, PRC and Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Material Technology and Engineering (NIMTE), Chinese Academy of Sciences (CAS) - Ningbo, 315201, PRC

^(a) zhanqf@nimte.ac.cn
^(b) runweili@nimte.ac.cn

Received: 6 September 2014
Accepted: 13 November 2014

Abstract

We demonstrated that the formation of magnetic conductive filaments in Co/ZnO/Fe sandwich structures can be employed to produce a nanoscale magnetic tunnel junction (MTJ) and control the tunneling magnetoresistance (TMR). The pristine Co/ZnO/Fe structures with a 100 nm thick ZnO layer do not exhibit any remarkable TMR. Under voltage sweeps performed on the sandwich devices, Co conductive filaments were grown in a ZnO layer, which leads to the formation of nanoscale Co/ZnO/Fe MTJs and the occurrence of TMR. In addition, a sign inversion of TMR was found in the nano-MTJs by carrying out the further voltage sweeps or varying the measuring bias voltage, which could be well understood in terms of the resonant tunneling caused by impurity scattering in a ZnO barrier.