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MA: Magnetismus

MA 20: Poster: Films(1-36) Transp(37-56) Ex.Bias(57-67) Spindyn(68-80) Micromag(81-95) Particle(96-109) Imag.+Surface(110-113) Spinelectr(114-122) Theory+Micromag(123-131) Spinstr+Aniso(132-142) MagMat(143-156) Meas(157,158) MolMag+Kondo(159-162) Postdead(163-)

MA 20.57: Poster

Dienstag, 28. März 2006, 15:15–19:15, P1

Strong temperature dependence of antiferromagnetic coupling in CoFeB/Ru/CoFeB — •N. Wiese^1,2, T. Dimopoulos^1,3, M. Rührig¹, and G. Reiss² — ¹Siemens AG Corporate Technology, CT MM 1, Erlangen, Germany — ²Universität Bielefeld, Nano Device Group, Bielefeld, Germany — ³ARC Seibersdorf research GmbH, Vienna, Austria

Due to their high tunneling magnetoresistance (TMR) of up to 70%, magnetic tunnel junctions (MTJ) with electrodes consisting of amorphous Co₆₀Fe₂₀B₂₀ have gained considerable interest for the use in applications, e.g. sensor applications or magnetoresistive random access memories (MRAM).

Furthermore it has been shown, that artificial ferrimagnets (AFi), consisting of two antiferromagnetically coupled layers of amorphous CoFeB separated by a thin nonmagnetic Ru-spacer, exhibit a stable coupling and a significant lower coercivity than AFi systems of polycrystalline CoFe materials.[1] Due to their magnetic properties, they are promising candidates also for the use as soft magnetic electrode in MTJs.[2]

Here we present the temperature dependence of saturation field (coupling) in dependence of Ru spacer thickness and net moment of the AFi. In good accordance to the theory, the investigated samples show a strong temperature behavior ∼ T/T₀/sinh(T/T₀), where T₀ = ℏ v_F/2 π k_B t_Ru. The Fermi velocity, v_F, evaluated for the investigated samples within this model, turns out to be in the order of 10⁷cm/s.

[1] N. Wiese et al., J. Magn. Magn. Mater. 290-291, 1427 (2005)

[2] N. Wiese et al., accepted for publication in J. Appl. Phys. (2005)