Magnetic and electrical transport properties of co-sputtered FexCu100-x composite films

The average surface roughness of the FexCu100-x composite films increases first and decreases latterly with the increase of Fe atomic fraction x. No Fe granules appear in the films, suggesting that Fe atoms disperse in the Cu matrix. At x ≤ 28.9, the films are superparamagnetic at room temperature. Below the blocking temperatures, the field-cooling magnetization decreases and the coercivity increases with the decrease of temperature. The electrical transport mechanism of the FexCu100-x composite films is metallic. The magnetoresistance (MR) decreases with the increase of x. Meanwhile, MR increases with the decrease of temperature at a certain x and increases significantly in the low-temperature range. At x = 8.7, the maximum MR reaches -13% at 3 K. The extraordinary Hall resistivity increases with the increasing x and the decreasing temperature. The low-temperature magnetic and MR characters are related to the antiferromagnetic coupling of spin-glass-like moments.