Magnetic ground states of Ce3TiSb5, Pr3TiSb5and Nd3TiSb5determined by neutron powder diffraction and magnetic measurements.

TheR3TiSb5ternary compounds, withRa light rare earth (La to Sm) have been reported to crystallize with the anti-Hf5CuSn3-type hexagonal structure (Pearson's symbolhP18; space-groupP63/mcm, N. 193). An early article that reported possible superconductivity in some of these intermetallic phases (namely those withR= La, Ce, and Nd) caught our attention. In this work, we have now refined the crystal structure of theR3TiSb5compounds withR= Ce, Pr and Nd by Rietveld methods using high-resolution neutron powder diffraction data. The magnetic ground states of these intermetallics have been investigated by low-temperature magnetization and high-intensity neutron diffraction. We find two different magnetic transitions corresponding to two related magnetic structures atTN1= 4.8 K (k1= [0, 1/2, 1/8]) andTN2= 3.4 K (k2= [0, 0, 1/8]), respectively for Ce3TiSb5. However, the magnetic ordering appears to occur following a peculiar hysteresis: thek2-type magnetic structure develops only after thek1-type phase fraction has first slowly ordered with time and the size of the ordered Ce3+magnetic moment has become large enough to induce the second magnetic transition. AtT= 1.5 K the maximum amplitude of the Ce moment in the coexisting phases amounts toµCe= 2.15 µB. For Nd3TiSb5an antiferromagnetic ordering belowTN= 5.2 K into a relatively simpler commensurate magnetic structure with a magnetic moment ofµNd= 2.14(3)µBand magnetic propagation vector ofk= [0, 0, 0], was determined. No evidence of superconductivity has been found in Nd3TiSb5. Finally, Pr3TiSb5does not show any ordering down to 1.5 K in neutron diffraction while an antiferromagnetic ground state is detected in magnetization measurements. There is no sign of magnetic contribution from Ti atoms found in any of the studied compounds.