Dresden 2009 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 16: Poster I

DS 16.31: Poster

Dienstag, 24. März 2009, 09:30–12:30, P5

Effect of annealing and thickness of MgO films on magnetoresistive and electrical properties of CoFeB/MgO granular system — •Khalid Mehmood Bhutta, Jan Schmalhorst, and Günter Reiss — Thin Films and Physics of Nano structures, Department of Physics, University of Bielefeld, 33615 Bielefeld Germany

Granular metals are inhomogeneous mixtures of metals and non-metals. Recently granular metals of ferromagnetic grains embedded in the matrix of oxides have been investigated because of their applications in electronic devices. The electrical and magnetic properties of such metals can be manipulated by the thickness of ferromagnetic and oxide layers. In the present work, the magnetic and electrical properties of CoFeB/MgO granular metal having various thicknesses of oxide layer as well as the effect of annealing temperature and time have been studied. The optimum value of GMR was achieved at 0.7nm MgO thickness. A nominal change in the MgO thickness strongly affects the Magnetoresistance of the granular metal. Multiple annealing steps at constant temperature of 250oC improve the GMR ratio. However, a deteriorated GMR ratio at the annealing temperature of 300oC points to the crystallization of CoFeB. Regarding the low temperature measurements, the electron transport follows the Mott’s Law of Variable Range Hopping. However, at temperature lower than 50 Kelvin a deviation from Mott’s Law has been observed.

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