Neutron powder diffraction study of magnetic order in geometrically frustrated triangular lattice: CeAuAl4Ge2

Recently the compounds with geometrically frustrated crystal structure have attracted considerable attention due to frustration induced quantum spin-liquid ground state. CeAuAl4Ge2, which crystallizes in a triangular lattice (rhombohedral, space group R-3m) structure, is reported to exhibit a phase transition near 1.4 K in heat capacity and electrical resistivity. The entropy is found to be only 52% of Rln2 near the transition temperature, but Rln2 at 15 K, indicating a presence of short-range ordering above 1.4 K. Initial interpretation for this phase transition is a magnetic ordering of an antiferromagnetic character. The Kondo hybridization as inferred from the electrical resistivity is almost negligible. In the rhombohedral structure of CeAuAl4Ge2, the Ce-moments form the equilateral triangle arrangement and hence are subject to geometrical frustration and could stabilize complex magnetic structure. Further investigations using neutron diffraction measurements are highly desired to determine the magnetic structure of this compound and the presence of short-range magnetic correlations above TN=1.4 K. We propose to carry out neutron powder diffraction measurements on CeAuAl4Ge2 using the WISH diffractometer to determine the magnetic structure of this geometrically frustrated compound and short-range correlations present above the phase transition as evident from the magnetic entropy.