Dresden 2017 – scientific programme

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MA: Fachverband Magnetismus

MA 66: Poster 3

MA 66.21: Poster

Friday, March 24, 2017, 09:30–13:00, P2-OG2

Comparative study of CoFeAlB and CoFeB FMR properties for spin torque devices — •Andres Conca¹, Thomas Meyer¹, Takafumi Nakano², Yasuo Ando², and Burkard Hillebrands¹ — ¹FB Physik and Landesforschungszentrum OPTIMAS, TU Kaiserslautern, Germany — ²Department of Applied Physics, Tohoku University, Japan

The magnitude of critical current required for switching in spin transfer torque (STT) devices is ruled by the product of the Gilbert damping parameter α and the square of the saturation magnetization M_s of the electrode material. Co₄₀Fe₄₀B₂₀ is dominantly used as free layer electrode in MgO-based MTJs. The material has a low α around 0.0042 but the large M_s hinders the use in STT devices. In this sense, research has been carried out to dope CoFeB alloys in order to reduce the magnetization without destroying the low damping properties. Here, we present results of the FMR properties of film series of Co₃₆Fe₃₆Al₁₈B₁₀ with different annealing temperatures. The dependence of the linewidth, α, and M_s have been obtained. Additional information regarding the exchange constant is gained through measurements of the perpendicular standing spin waves (PSSW). An additional CoFeB series has also been measured for comparison. The data proves a significant reduction of M_s and the exchange constant in CoFeAlB compared to CoFeB while α remains similar or even smaller for most of the annealing temperatures. The evolution of α with annealing shows a different behavior for both materials. This proves the suitability of CoFeAlB for STT devices. Support by M-era.Net and HEUMEM is acknowledged.