Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf
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Electrical field-controlled ON-OFF ferromagnetism in single metal oxide filmsLiedke, M. O.ORC; Butterling, M.; Quintana, A.; Menéndez, E.; Hirschmann, E.; Sireus, V.; Nogués, J.; Sort, J.; Wagner, A.ORC; Elsherif, A. G. A.
With respect to applications, substituting electric currents, which are nowadays used to operate spintronic devices, with electric fields, would result in a reduction of both the energy consumption and cost . Co3O4 is a candidate for a tunable, non-volatile energy-efficient functional material whose magnetic properties can be controlled by electric voltage. In our current investigations the as-grown Co3O4 films consist of a paramagnetic (PM) phase only, which is transformed to a ferromagnetic (FM) state by electrolyte-gated and defect-mediated O and Co transport. A negative voltage reduces Co3O4 to Co (FM: ON), resulting in a phase separated material with Co- and O-rich regions. Applying a positive bias, the process is reversed oxidizing Co back to Co3O4 (PM: OFF). We will show that atoms migration is driven by rather complex vacancy states and a clear increase of the grain boundaries volume after negative biasing assists to O transport. Moreover, concomitantly with the PM phase transition due to the positive biasing the structural defects picture reverses to a large extent as well, which manifests as reduction in volume of both vacancy clusters and grain boundaries. Doppler broadening and positron annihilation lifetime spectroscopy have been used as an in-situ probe of electric field driven ionic transport of Co and O via different type of defects in Co3O4 systems .
 Y. Shiota, et al. Nature Mater. 11, 39 (2012)
 A. Quintana, E. Menéndez, M. O. Liedke, M. Butterling, A. Wagner, et al. ACS Nano 12, 10291 (2018)
Keywords: positron, positron annihilation spectroscopy, AIDA, magnetism, voltage
“From Matter to Materials and Life” (MML), 12.02.2019, Dresden, Deutschland
Invited lecture (Conferences)
15th International Workshop on Slow Positron Beam Techniques & Applications (SLOPOS-15), 02.09.2019, Prague, Czech Republic
The European Materials Research Society (E-MRS) Fall Meeting, 16.09.2019, Warsaw, Poland