Neutron diffraction and 119Sn Moessbauer study of Sm3Ag4Sn4

The magnetic properties of Sm3Ag4Sn4 have been investigated using bulk magnetization, Sn-119 Mossbauer spectroscopy and neutron diffraction. We find that the Neel temperature (T-N) is 26.0( 5) K, well above the value of similar to 9 K previously determined using magnetic susceptibility measurements. Neutron diffraction data indicate that the Sm moments most likely adopt either the I(P)mm' m or I(P)mmm' magnetic space groups, neither of which allows order at the 2d site, in marked contrast to the vast majority of other compounds in the R3T4X4 family. Transferred hyperfine field models suggest that the I(P)mmm is the only group that is consistent with the 119Sn Mossbauer results. We derive a samarium moment of 0.47 +/- 0.10 mu(B) on the Sm 4e site at 3 K. 119Sn Mossbauer spectroscopy shows that the system undergoes a spin reorientation transition at 8.3(3) K, where the moments rotate towards the a-axis.