Enhanced magnetic anisotropy and high hole mobility in magnetic semiconductor Ga_1-x-y Fe _x Ni _y Sb

(Ga,Fe)Sb is a promising magnetic semiconductor (MS) for spintronic applications because its Curie temperature (T-C) is above 300 K when the Fe concentration is higher than 20%. However, the anisotropy constant K-u of (Ga,Fe)Sb is below 7.6 x 10(3) erg/cm(3) when Fe concentration is lower than 30%, which is one order of magnitude lower than that of (Ga,Mn)As. To address this issue, we grew Ga1-x-yFexNiySb films with almost the same x (approximate to 24%) and different y to characterize their magnetic and electrical transport properties. We found that the magnetic anisotropy of Ga0.76-yFe0.24NiySb can be enhanced by increasing y, in which K-u is negligible at y = 1.7% but increases to 3.8 x 10(5) erg/cm(3) at y = 6.1% (T-C = 354 K). In addition, the hole mobility (mu) of Ga1-x-yFexNiySb reaches 31.3 cm(2)/(Vs) at x = 23.7%, y = 1.7% (T-C = 319 K), which is much higher than the mobility of Ga1-xFexSb at x = 25.2% (mu = 6.2 cm(2)/(Vs)). Our results provide useful information for enhancing the magnetic anisotropy and hole mobility of (Ga,Fe)Sb by using Ni co-doping.