Co2V0.67Fe0.33Al full-Heulser alloy films were fabricated on an MgO (100) single crystalline substrate by using two different heat treatments: substrate heating and post-annealing. Ultra-high-vacuum dc magnetron sputtering was used to prepare the sample. The L21 structure was obtained when the substrate temperature (Ts) was 500°C. For the same sample, the magnetic moment per formula unit showed the highest value of 2.4 μB at 5 K. There were small differences between the samples fabricated by substrate heating and post-annealing in terms of their structural and magnetic properties. A magnetic tunnel junction (MTJ) using Co2V0.67Fe0.33Al as a bottom electrode was fabricated. A larger tunnel magnetoresistance (TMR) was obtained by substrate heating than post-annealing with a maximum value of 28% at RT and 50% at 5 K when the Co2V0.67Fe0.33Al was sputtered at Ts = 500°C. We found that there is an intimate relationship between the lattice constant of Co2V0.67Fe0.33Al and the TMR.
