Annealed coated air-stable cobalt--rare earth alloy particles

A process is described for producing novel air-stable coated particles of a magnetic transition metal-rare earth alloy. An organometallic compound which decomposes at a temperature below 5000C is heated to produce a metal vapor which is contacted with particles of a transition metal-rare earth alloy to deposit a metal coating thereon. The coated particles are heated at a temperature ranging from 50 to 2000C for a period of time sufficient to increase their intrinsic coercive force by at least 10 percent. (U.S.)