Magnetic ordering in DyMn 6− xCr xSn 6 ( [formula omitted]) compounds studied by neutron diffraction and magnetic measurements

Abstract

We have studied the effect of Cr substitution on the magnetic ordering of the hexagonal pseudoternary DyMn 6− x Cr x Sn 6 ( x=1, 2 ) compounds by neutron diffraction and magnetic measurements at temperatures between 1.5 and 360 K. Below T C each of the magnetic sublattices displays a ferromagnetic moment arrangement. The moments of the two sublattices are coupled antiferromagnetically with a temperature-dependent moment orientation at lower temperatures ( T t ). For the compound with x=1 magnetic ordering occurs below 355 K and T t =260 K. For the compound with x=2 magnetic ordering occurs below 245 K and T t =220 K. Between T t and T C both compounds display planar anisotropy. Below T t a partial rotation of the moment angle ( φ c ) with c sets in. The value of φ c decreases smoothly with temperature from 90° to about 45–50° between T t and T i ≈100–120 K and retains the same angle down to 1.5 K. The ordered moment values at 1.5 K are 8.28(9) and 8.13(8) μ B per Dy atom and 2.12(5) and 1.79(4) μ B per (Mn/Cr) atom for the two compounds DyMn 5CrSn 6 and DyMn 4Cr 2Sn 6, respectively. Alloying with the almost non-magnetic Cr leads to a substantial decrease of the ordering and of the spin reorientation temperatures as well as a reduction of the ordered Dy moment value compared to the compound DyMn 6Sn 6.