Magnetic structure and susceptibility ofCoSe2O5: An antiferromagnetic chain compound

Abstract

CoSe 2 O 5 has a crystal structure consisting of zigzag chains of edge shared CoO 6 octahedra running along the c axis with the chains separated by Se 2 O 5 2− units. Magnetic-susceptibility measurements indicate a transition at 8.5 K to an ordered state. We investigate the nature of this magnetic order using magnetization and specific-heat measurements, in addition to powder neutron diffraction. A transition to long-range antiferromagnetic order is found below T N = 8.5 K as identified by magnetic-susceptibility and heat-capacity measurements, and the emergence of magnetic Bragg reflections with a propagation vector k = 0. The low-field magneticsusceptibility data indicate the presence of weak ferromagnetism in the antiferromagnetic ordered state which saturates in very small fields. Heat-capacity measurements at low temperatures indicate that only about half the configurational entropy is released at T N . The functional form of the heat capacity below T N suggests the presence of a gap of 6.5 K in the magnon dispersion. The refined magnetic structure shows that the moments align perpendicular to the c axis, and tilting alternately by +14°and −14°with respect to the a axis.

Single crystal magnetic structure and susceptibility of CoSe2O5

“…The invariance of the fit with respect to having a coefficient on the ψ 2 8 basis vector of Table 2 could be the reason why the magnetic structure from the current analysis is different from the one determined using powder methods in Ref. 6. Both nuclear and magnetic reflections were therefore included in order to fit any possible c-axis component.…”

“…[5] Previous work on polycrystalline powders of CoSe 2 O 5 reported a canted antiferromagnetic ground state below an ordering temperature of 8.5 K. Low-field magnetization measurements also indicated signs of weak ferromagnetism, but no explanation for this behavior was suggested. [6] Here, we perform a detailed investigation into the anisotropic magnetic properties of CoSe 2 O 5 . Using neutron scattering on single crystals, we find no evidence for canting of the magnetic moments previously seen in powdered samples, but instead find a uniformly collinear antiferromagnetic structure within and between the chains with moments oriented along the a-axis.…”

Magnetic structure and properties of NaFeSO4F and NaCoSO4F

“…Such a result is a reflection of the unquenched orbital contribution to the magnetic moment that was identified in the Curie-Weiss analysis of the temperature-dependent magnetic susceptibility data and is in good agreement with what has typically been seen for Co 2+ ions. [31][32][33] The resulting magnetic structures of NaFeSO 4 F and NaCoSO 4 F are gathered in Table IV and illustrated in Fig. 5.…”

Ising-like antiferromagnetism on the octahedral sublattice of a cobalt-containing garnet and the potential for quantum criticality

“…Starting at 4 K, however, a distinct fielddependent magnetic transition begins to evolve around 25 kOe, which moves to fields of 40 kOe and 50 kOe as the temperature is decreased further. Field-dependent metamagnetic transitions such as this have been observed in several other Co-based compounds, [19][20][21] and is typically attributed to the magnetic field strength becoming strong enough to overcome the single-ion anisotropy of the moments and drive the order towards a field polarized state. [19,20] The field-and temperature-dependence of the magnetism encouraged us to explicitly map out these transitions using specific heat measurements as shown in Figure 4 (a).…”

“…Field-dependent metamagnetic transitions such as this have been observed in several other Co-based compounds, [19][20][21] and is typically attributed to the magnetic field strength becoming strong enough to overcome the single-ion anisotropy of the moments and drive the order towards a field polarized state. [19,20] The field-and temperature-dependence of the magnetism encouraged us to explicitly map out these transitions using specific heat measurements as shown in Figure 4 (a). In the absence of a magnetic field, a sharp lambda-like anomaly evolves at 6 K, in very good agreement with the temperature-dependent magnetic susceptibility data.…”