Magnetic semiconductors have been investigated more and more actively, and have become a matter of interest for many researchers. To realize optical spintronic devices, it is strongly desirable that the semiconducting materials have magnetism with high Curie temperature as well as excellent optical (luminescence) properties. It is also necessary and of interest to create transparent magnetic semiconductors that can show optical emission. The magnetic and optical properties of a novel magnetic semiconductor, Cr-doped ZnO, were examined. All Cr-doped ZnO thin films were grown by the Ar-F excimer laser ablation (pulsed laser deposition, PLD) method. The room temperature photoluminescence peaks are very sharp and there is no deep-level emission. Prepared p-i-n diodes consisting of La0.85Sr0.15MnO3/SrTiO3/Zn1-xCrxO triple-heterostructures exhibited clearly the rectifying I-V curves. (C) 2003 Elsevier Science B.V. All rights reserved.