Enhancing s, p-d exchange interactions at room temperature by carrier doping in single crystalline Co_0.4Zn_0.6O epitaxial films

Magnetic doping of semiconductors has been actively pursued because of their potential applications in the spintronic devices. Central to these efforts is a drive to control the mutual interactions between their magnetic properties (supported by d electrons of the magnetic ions) and their semiconductor properties (supported by s and/or p electrons) at room temperature (RT). Despite the long, intensive efforts, the experimental evidence of thermally robust s, p-d coupling in a semiconductor remains scarce and controversial. Here, we report the enhancement of RT ferromagnetic s, p-d exchange interaction by means of carrier doping in single crystalline Co_0.4Zn_0.6O epitaxial films with a high Co concentration. Magneto-transport measurements reveal that spin-polarized conducting carriers are produced at RT and are increased with the carrier density through Ga³⁺ doping, owing to the s, p-d coupling between Ga (4s), O (2p), and Co (3d) orbitals. With the ability to individually control carrier density and magnetic doping, single crystalline Ga(Co, Zn)O films can lay a solid foundation for the development of practical semiconductor spintronic devices operable at RT.