Room temperature magnetic hardening in mechanically milled ferromagnetic-antiferromagnetic composites

Enhancements in coercivity, squareness and energy product have been obtaine d at room-temperature by mechanically milling mixtures of ferromagnetic (FM ) (Co) and antiferromagnetic (AFM) (NiO) powders. All these effects decreas e with increasing temperatures, up to T = 600 K, just above the Neel temper ature of the antiferromagnet. Due to the competition between coercivity enh ancement and reduction of saturation magnetization in AFM/FM mixtures, alth ough the maximum coercivity enhancement has been found for (AFM)1:1(FM) wei ght ratio, the maximum energy product is obtained for composites with large r FM content, i.e. (AFM)2:3(FM). (C) 2000 Elsevier Science B.V. All rights reserved.