The magnetic structure of Co(NCNH)2 as determined by (spin-polarized) neutron diffraction

Abstract

The magnetic structure of Co(NCNH) 2 has been studied by neutron diffraction data below 10 K using the SPODI and DNS instruments at FRM II, Munich. There is an intensity change in the (1 1 0) and (0 2 0) reflections around 4 K, to be attributed to the onset of a magnetic ordering of the Co 2+ spins. Four different spin orientations have been evaluated on the basis of Rietveld refinements, comprising antiferromagnetic as well as ferromagnetic ordering along all three crystallographic axes. Both residual values and supplementary susceptibility measurements evidence that only a ferromagnetic ordering with all Co 2+ spins parallel to the c axis is a suitable description of the low-temperature magnetic ground state of Co(NCNH) 2 . The deviation of the magnetic moment derived by the Rietveld refinement from the expectancy value may be explained either by an incomplete saturation of the moment at temperatures slightly below the Curie temperature or by a small Jahn–Teller distortion. The magnetic ground state of Co(NCNH) 2 has been clarified by (spin-polarized) neutron diffraction data at low temperatures. Intensity changes below 4 K arise due to the onset of ferromagnetic ordering of the Co 2+ spins parallel to the c axis, corroborated by various (magnetic) Rietveld refinements. • Powderous Co(NCNH) 2 has been subjected to (spin-polarized) neutron diffraction. • Magnetic susceptibility data of Co(NCNH) 2 have been collected. • Below 4 K, the magnetic moments align ferromagnetically with all Co 2+ spins parallel to the c axis. • The magnetic susceptibility data yield an effective magnetic moment of 4.68 and a Weiss constant of −13(2) K. • The ferromagnetic Rietveld refinement leads to a magnetic moment of 2.6 which is close to the expectancy value of 3.