MAGNETIC-PROPERTIES OF THE SM1-XCEXMN2GE2 SYSTEM

Magnetic properties of polycrystalline Sm1-xCexMn2Ge2 (0 less than or equal to x less than or equal to 1) compounds have been studied by mag netic susceptibility measurements. A magnetic phase diagram has been c onstructed. The SmMn2Ge2 sample shows re-entrant ferromagnetism with a ferromagnetic (FM) transition at T-1 = 341 K, a FM to antiferromagnet ic (AF) transition at T-2 = 144 K, an AF to FM transition at T-3 = 105 K, and then a Sm-ordering-related FM transition at T-sm approximate t o 20 K. As x increases, (i) T-1 and T-2 decrease, (ii) T-3 increases i nitially and then decreases beyond x = 0.011, and (iii) T-sm remains u nchanged up to x = 0.1 and then decreases rapidly. The AF phase is des troyed at x = 0.011. The AF region width Delta T-AF. (= T-2 - T-3) var ies with R-Mn-Mn(a) at a rate about ten times as fast as that in Sm1-x GdxMn2Ge2. Our results suggest that T-3 can be affected by both the in tralayer Mn-Mn distance and the spin disorder in the rare-earth layers .