Effect of film thickness on the electrical transport in Co2FeAl0.5Si0.5 thin films

Abstract

The effect of film thickness on the structural- and electrical-properties is investigated in Co2FeAl0.5Si0.5 (CFAS) thin films of thickness, t, in the range 12–75 nm. These films are grown by ultrahigh vacuum dc magnetron sputtering on Si(100) substrates with SiO2 buffer layer (300 nm), at the substrate temperature of 500 ◦C. The GIXRD patterns reveal that B2 structural order decreases with increasing t. The film with t = 75 nm has sizable A2 disorder. Irrespective of t, ρ(T, H = 0) goes through a minimum at Tmin. An elaborate quantitative analysis of the ρ(T, H = 0) data, taken over the temperature range 5 K to 300 K, demonstrates that the electron-diffuson (e–d) and weak localization (WL) effects (responsible for the negative temperature coefficient of resistivity (TCR) for T < Tmin) compete with the electron-magnon (e–m) and electron–phonon (e–p) scattering (positive TCR) contributions to produce a minimum at Tmin. Residual resistivity, ρ5K, and the e–d, wl, e–m and e–p scattering contributions to ρ(T, H = 0), ρe–d, ρwl, ρe–m and ρe–p, all go through a minimum at t = 50 nm. Regardless of t, the thermal renormalization of the spin-wave stiffness makes a significant contribution to ρe–m.