Magnetic properties and magnetic structures in R3Ni2In4 (R = Tb–Tm)

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The R 3 Ni 2 In 4 (R = Tb–Tm) ternary indides have been investigated by X-ray and neutron powder diffraction as well as magnetometric measurements. The compounds crystallize in the hexagonal Lu 3 Co 2 In 4 -type structure (a lower-symmetry derivative of the ZrNiAl-type one). Er 3 Ni 2 In 4 has been found paramagnetic down to 1.6 K while all other samples order antiferromagnetically below 23.3 K (R = Tb), 9.7 K (R = Dy), 3.3 K (R = Ho) and 3.2 K (R = Tm). The magnetic unit cell in R 3 Ni 2 In 4 (R = Tb, Dy) is doubled along the c-axis with respect to the crystal one (propagation vector k → = [ 0,0 , 1 2 ] ). The magnetic moments lie in the basal plane and form a “triangular” magnetic structure as often found in geometrically frustrated antiferromagnets. The magnetic order in Ho 3 Ni 2 In 4 consists of two components: a commensurate one which is described above ( k → = [ 0,0 , 1 2 ] ) and an incommensurate one ( k → = [ 1 3 , 1 3 , k z ] where k z = 0.271 ( 11 ) at 1.6 K). The magnetic moments of the incommensurate component are inclined at a small angle with respect to the basal plane and form a non-collinear magnetic structure. The magnetic structure in Tm 3 Ni 2 In 4 is a commensurate one ( k → = [ 1 3 , 1 3 , 1 2 ] ) with magnetic moments within the basal plane forming a non-collinear “triangular” structure. A determination of magnetic structures is supported by detailed symmetry analysis. • R 3 Ni 2 In 4 (R = Tb–Tm), except Er 3 Ni 2 In 4 , are found antiferromagnetic at low temperatures. • Er 3 Ni 2 In 4 remains paramagnetic down to 1.6 K. • Only rare earth atoms carry magnetic moments. • In most cases the magnetic moments are confined to the basal plane. • “Triangular” magnetic structures, typical of geometrical frustration, are observed.