Room temperature magnetic hardening in mechanically milled ferromagnetic-antiferromagnetic composites

Enhancements in coercivity, squareness and energy product have been obtained at room-temperature by mechanically milling mixtures of ferromagnetic (FM) (Co) and antiferromagnetic (AFM) (NiO) powders. All these effects decrease with increasing temperatures, up to T = 600 K, just above the Neel temperature of the antiferromagnet. Due to the competition between coercivity enhancement and reduction of saturation magnetization in AFM/FM mixtures, although the maximum coercivity enhancement has been found for (AFM)1:1(FM) weight ratio, the maximum energy product is obtained for composites with larger FM content, i.e. (AFM)2:3(FM).