Thickness-, Composition-, and Magnetic-Field-Dependent Complex Impedance Spectroscopy of Granular-Type-Barrier Co/Co-Al2O3/Co MTJs
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The alternating-current (ac) electrical properties of granular-type-barrier magnetic tunnel junctions (GBMTJs) based on Co/Cox(Al2O3)1−x(t)/Co trilayer structures have been studied using complex impedance spectroscopy (CIS). Their CIS characteristics were investigated in external magnetic fields varying from 0 kOe to 3 kOe as a function of Co composition x at 10 at.%, 25 at.%, and 35 at.%, with barrier layer thickness t of 20 nm to 90 nm. The influence of these factors on the behaviors of the ac impedance response of the GBMTJs was deeply investigated and attributed to the dielectric or conducting nature of the Co-Al2O3 barrier layer. The most remarkable typical phenomena observed in these behaviors, even appearing paradoxical, include lower impedance for thicker t for each given x, a declining trend of Z with increasing x, a clear decrease of Z with H, and especially a partition of Z into zones according to the H value. All these effects are analyzed and discussed to demonstrate that diffusion-type and mass-transfer-type phenomena can be inferred from processes such as spin tunneling and Coulomb or spin blockade in the Co-Al2O3 barrier layer.
KeywordsGranular-type-barrier MTJ hybrid-type MTJ complex impedance spectroscopy impedance response ac spin-dependent transport
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- 14.J. Barnaś and I. Weymann, J. Phys.: Condens. Matter 20, 423202 (2008).Google Scholar
- 22.J.R Macdonald and W.B. Johnson, Impedance Spectroscopy—Theory, Experiment, and Applications, 2nd edn., ed. By E. Barsoukov, J.R. Macdonald (Wiley, Hoboken, NJ, 2005). pp. 1–26.Google Scholar
- 28.N. Bonanos, B.C.H. Steele, and E.P. Butler, Impedance Spectroscopy—Theory, Experiment, and Applications, 2nd edn, eds. by E. Barsoukov and J. R. Macdonald (Wiley, Hoboken, NJ, 2005), pp. 205–263.Google Scholar
- 29.C. Derek Sinclair, Bol. Soc. Esp. Cerám. Vidrio 34, 55 (1995).Google Scholar