Thermal and electrical characterization of Cu/CoFe superlattices

Yang, Y.; Liu, W.; Asheghi, M.
April 2004
Applied Physics Letters;4/19/2004, Vol. 84 Issue 16, p3121
Academic Journal
The present work is directed at thermal and electrical characterization of the Cu/CoFe multilayer, which is made of extremely thin periodic layers, using steady-state Joule heating and thermometry in suspended bridges in the temperature range of 50–300 K. The total thickness of the layer is ds=144 nm, while the thickness of individual repeats are 12 and 21 Å for CoFe and Cu layers, respectively. The experimental data for thermal conductivity of a 144-nm-thick single Cu layer is also presented for comparison. The experimental data indicates that the spin-dependent electron scattering at the Cu/CoFe interface contributes to a strong reduction in thermal conductivity of these layers compared to the bulk values. The calculated Lorenz numbers (from the thermal and electrical conductivity data) varies by nearly a factor 2 from 4×10-8 W Ω K-2 at 50 K to 1.8×10-8 W Ω K-2 at 300 K and is different from the free electron value of L0=2.45×10-8 W Ω K-2. This implies that the Wiedemann-Franz law does not hold for Cu/CoFe thin films. © 2004 American Institute of Physics.


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