Study of the antiferromagnetic phase in Sm(Mn1-xCrx)(2)Ge-2

Magnetic and thermal expansion measurements have been carried out on the polycrystalline Sm(Mn1-xCrx)(2)Ge-2 samples to see how the antiferromagnetic (AFMII) region in SmMn2Ge2 is affected by Cr substitution. It is found that the antiferromagnetic region disappears for samples with less than 2 at.% of Cr. Sharp changes in the thermal expansivity (Delta l/l) at FMI-AFMII and AFMII-FMII transitions are observed, indicating first order transitions. The decrease in relative thermal expansivity at the two transitions with the increase of Cr concentration is related to the decrease in the stability and the temperature-range of the AFMII phase observed in magnetization measurements. A spin reorientation transition (T-SR) has been observed for x=0, at 148 K. It is found that the T-SR increases with the increase of Cr concentration. A magnetic phase diagram as a function of Cr concentration in Sm(Mn1-xCrx)(2)Ge-2 has been constructed.