  This work presents results for the magnetic properties of the compound GeTe
doped with 3d transition metals V, Cr and Mn from the viewpoint of potential
application in spintronics. We report a systematic density-functional study of
the electronic structure, magnetic and cohesive properties of these ternary
compounds in both rock salt and zinc blende structures. In both cases, it is
the Ge sublattice that is doped with the three transition metals. Some of these
compounds are found to be half-metallic at their optimized cell volumes. For
these particular cases, we calculate both exchange interactions and the Curie
temperatures in order to provide some theoretical guidance to experimentalists
trying to fabricate materials suitable for spintronic devices. Discussions
relating our results to the existing experimental studies are provided whenever
applicable and appropriate. Apparent discrepancy between experimental
observations and our theoretical result for the case of Mn-doping is discussed
in detail, pointing out various physical reasons and possible resolutions of
the apparent discrepancy.
