Magnetic ground states of Ce3TiSb5, Pr3TiSb5 and Nd3TiSb5 determined by neutron powder diffraction and magnetic measurements

Abstract The R 3 TiSb 5 ternary compounds, with R a light rare earth (La to Sm) have been reported to crystallize with the anti-Hf 5 CuSn 3 -type hexagonal structure (Pearson’s symbol hP 18; space-group P 6 3 / mcm , N. 193). An early article that reported possible superconductivity in some of these intermetallic phases (namely those with R = La, Ce, and Nd) caught our attention. In this work, we have now refined the crystal structure of the R 3 TiSb 5 compounds with R = 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 at T N1 = 4.8 K ( k 1 = [0, 1/2, 1/8]) and T N2 = 3.4 K ( k 2 = [0, 0, 1/8]), respectively for Ce 3 TiSb 5 . However, the magnetic ordering appears to occur following a peculiar hysteresis: the k 2 -type magnetic structure develops only after the k 1 -type phase fraction has first slowly ordered with time and the size of the ordered Ce 3+ magnetic moment has become large enough to induce the second magnetic transition. At T = 1.5 K the maximum amplitude of the Ce moment in the coexisting phases amounts to μ Ce = 2.15 μ B . For Nd 3 TiSb 5 an antiferromagnetic ordering below T N = 5.2 K into a relatively simpler commensurate magnetic structure with a magnetic moment of μ Nd = 2.14(3) μ B and magnetic propagation vector of k = [0, 0, 0], was determined. No evidence of superconductivity has been found in Nd 3 TiSb 5 . Finally, Pr 3 TiSb 5 does 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.