[Zurück]

M. Puydinger dos Santos, S. Barth, F. Béron, K. Pirota, A. Pinto, J. Sinnecker, S. Moshkalev, J. Diniz, I. Utke:
"Magnetoelectrical Transport Improvements of Postgrowth Annealed Iron-Cobalt Nanocomposites: A Possible Route for Future Room-Temperature Spintronics";
ACS Applied Nano Materials, 1 (2018), 1; S. 3364 - 3374.

Focused-electron-beam-induced deposition (FEBID) constitutes a direct-writing maskless technique, which has been employed to prepare nanodots, nanolines, as well as laminar and even three-dimensional nanostructures with potential in many technological fields. Here, we report direct-writing of functional nanostructures with the HFeCo₃(CO)₁₂ bimetallic carbonyl precursor. The metal content as well as the magnetotransport properties of Fe-Co-C-O deposits were reproducibly tuned upon ex situ postgrowth annealing at 100, 200, and 300 °C in a high-vacuum system. The atomic composition obtained by energy-dispersive X-ray spectroscopy (EDX) analysis revealed that carbonyl groups release during annealing, although principally sole oxygen is released from the deposits, yielding an atomic ratio of Co:Fe:C:O = 52:17:22:9 with respect to the atomic composition of as-grown Co:Fe:C:O = 41:13:26:20. Interestingly, the amorphous carbon contained in the as-grown material turns into graphite nanocrystals with an average size of around 11 nm with annealing at moderate temperatures, as suggested by Raman analysis. These compositional and microstructural changes permit tuning the deposits´ electrical resistivity over 2 orders of magnitude from 4200 down to 65 μΩ cm. The anisotropic magnetoresistance (AMR) of the annealed deposits is about 1.2%, which represents the highest value so far reported for FEBID-grown materials. In addition, as a key feature for technological applications of the postgrowth treatment presented herein, the magnetotransport properties of the nanosized FEBID material degrade minimally after being stored at ambient conditions for more than one year. It turns out that both the iron and cobalt are protected from being oxidized under ambient atmosphere by the graphitic matrix. Furthermore, the incorporation of carbon atoms in ferromagnetic films allows for consistent improvements in their magnetic coercivity and reversing fields. This makes our material especially interesting and advantageous for applications in high-density magnetic recording devices, nanoelectronics, nanoelectromechanical system-based (NEMS-based) sensors, and logic devices.

http://dx.doi.org/10.1021/acsanm.8b00581