NEW RARE-EARTH INTERMETALLIC PHASES R(3)(FE,M)(29)X(N) - (R=CE, PR, ND, SM, GD, M=TI, V, CR, MN, AND X=H, N, C)

New rare-earth (R), iron-rich ternary intermetallic compounds of the form R3(Fe,M)29 with the monoclinic Nd3(Fe,Ti) 29 structure (space group P21/c, #14, Z=2) have recently been shown to form with R=Ce, Nd, Pr, Sm, and Gd, and M=Ti, V, Cr, and Mn. This novel structure is derived from the alternate stacking of Th2Zn 17 and ThMn12-type segments and contains two R sites and fifteen Fe(M) sites. Reported Curie temperatures of the 3:29 compounds range from 296 K (R=Ce, M=Cr) to 524 K (R=Sm, M=V). The 3:29 compounds all show improved magnetic properties after interstitial modification with H or N; in particular, room-temperature coercivity has been reported in Sm 3(Fe,Ti)29N5, making this compound a candidate for possible permanent-magnet applications. In this article we will review the work carried out to date on the 3:29 compounds.