I had a visiting student, Dr. Parmanand Sharma (the paper’s first author) from the University of Delhi, who was finalizing his thesis work by carrying out pulsed laser deposition of thin films of ZnO for sensor applications. During that time, we also had Prof. Gillian Gehring from the University of Sheffield as a Visiting Professor, who was keen to use our capabilities in pulsed laser deposition technique to deposit thin films of room-temperature ferromagnetic semiconductors (the so called DMS's).

We knew of the theoretical prediction by Dietl that ZnO doped with Mn would be a room-temperature ferromagnet. These factors triggered our interest, and since we had considerable experience with ZnO, and knew the complexities of MnO at higher temperatures, we were successful in producing the first room-temperature transparent Mn-doped ZnO ferromagnetic films. Then we contacted our colleagues in Uppsala for theoretical calculations and they became our coauthors in the paper.

Our results clearly demonstrated the importance of low-temperature processing of complex oxide materials. It confirmed the theoretical expectations. We also demonstrated that the above properties can be obtained in powder, bulk, as well as thin films in particular, which are important for applications in spintronics. The challenge to exploit these findings to develop new applications is now open.

We are routinely reproducing thin films as well as powder and bulk materials of Mn-doped ZnO which are ferromagnetic above room temperature. Since our paper appeared there have been many reports confirming our results. There are also some reports describing the inability to reproduce our results, especially in powders produced by chemical techniques. This, we know, is because of the inadequacies in the processing of these materials. We have shown recently that sometimes, depending on the particle size, the powder obtained may not be ferromagnetic; however, when the powders are pelletized and PLD deposited, we obtain well-oriented room-temperature ferromagnetic thin films from these very powders. It is very important that Mn is introduced substitutionally into ZnO and that it is in the 2+ Valence state.

It is well known that the most studied material, Mn-doped GaAs, is ferromagnetic only in the thin-film form although at about 100K below room temperature. Any continued skepticism or doubts which may exist are, we believe, due to man-made problems with the processing of these materials.

Anyway, it is satisfying to note the enormous interest and significant references to our paper in Nature Materials. Certainly, our paper has initiated a significant level of scientific activity in these materials.

Since our first reports we have now discovered a number of doped ZnO-based materials which are ferromagnets above room temperature.

Yes, we are now testing sensors based on the piezo-electric-related properties of these materials. We have also seen some promising optical properties which we plan to exploit for applications.

For future electronic applications, we need to tailor the material to obtain the full moment of Mn, and also develop the magnetic coercivities to functional levels. These are our main challenges which we will solve by co-doping and other processing procedures.

We are optimistic that sometime in the near future, before five years, novel optical and electronic devices can be developed exploiting the manifestations of spins of the electrons in these materials.