Magnetic Properties of Some Sm(2-x)R(x)Co(17-y)Mn(y) Intermetallic Compounds,

Current military requirements are leading to the development of a new generation of microwave and millimeter wave tubes whose magnetic circuits need permanent magnets with the following properties: energy products in excess of 30 MGOe, low reversible temperature coefficients of magnetization, α, and linear demagnetization curves. Rothwarf, Leupold and Jasper (1) have discussed approaches to the design of such magnetic circuits and the synthesis of suitable permanent magnet materials. Some of our preliminary efforts to attain compounds with such properties were also recently reported (2, 3) and reviewed (4). In the present paper we review our earlier work and report new results on the use of heavy rare earth substituents for some samarium in an attempt to achieve intrinsically temperature compensated 2–17 magnets. Such an approach was first successfully applied to SmCo5 by Benz, Laforce and Martin (5). The systems being reported on are Sm2−xRxCo17−yMny, where R=Gd, Er and Dy. The manganese is being used since we had previously found (6) that its presence in the quaternary system Sm2Mn(Co,Fe)16 significantly enhanced the anisotropy fields HA over those measured for the corresponding compounds in the ternary system Sm2(Co,Fe)17. Also Nagel (7) found that using manganese or chromium substituents for cobalt in the Sm2Co17 and Sm2(Co,Fe)17 compounds significantly enhances their coercivities and energy products.