Magnetic and magneto-transport properties of ZnO : Ni films

Magnetic semiconductor (MS), Ni doped ZnO film was fabricated by pulsed las er deposition method on sapphire (0 0 0 1) substrates. Ni dissolves until 2 5 at% into ZnO by low temperature growth technique. Lattice constant c once increases with increasing Ni content and has maximum point at the Ni conte nt of 5 at%, and then it suddenly decreases. In all the Ni content range, t he films exhibits n-type conduction. With increasing the Ni content, the ca rrier density and mobility decrease. ZnO films with the Ni content range fr om 3 to 25 at% exhibit ferromagnetic behavior at 2 K. At 30 K, the magnetiz ation against applied magnetic field shows superparamagnetic behavior and i t maintains at least up to 300 K. To study the effect of carrier density, A l was additionally doped. The effect of carrier density and Ni content on t he structure, magnetic and magneto-transport behaviors are described. (C) 2 001 Elsevier Science B.V. All rights reserved.