Method for increasing the effectiveness of a magnetic field for magnetizing cobalt-rare earth alloy

Claim 1

A process for substantially magnetizing a cobalt-rare earth alloy sintered product wherein the pores are substantially non-interconnecting and having a density ranging from about 87 to 100 percent and consisting essentially of compacted particulate alloy consisting essentially of a composition ranging from a single solid Co 5 R phase to a Co 5 R phase and a second solid CoR phase in an amount up to about 30 percent by weight of said product and richer in rare earth metal content than said Co 5 R phase, where R is a rare earth metal or metals, said product having an intrinsic coercive force H ci in excess of 5000 oersteds and characterized by a significant loss in its room temperature intrinsic coercive force H ci at a depressed temperature ranging from -25° C. to -200° C., which comprises cooling said sintered product to a depressed temperature ranging from -25° C. to -200° C. at which its intrinsic coercive force H ci is significantly lower than at room temperature, applying said sintered product at said depressed temperature a magnetizing field ranging from 500 oersteds to 20,000 oersteds substantially along its easy axis of magnetization and warming said sintered product in said magnetizing field to room temperature.