Magnetic behaviour of synthetic Co₂SiO₄

Abstract

Synthetic Co(2)SiO(4) crystallizes in the olivine structure (space group Pnma) with two crystallographically non-equivalent Co positions and shows antiferromagnetic ordering below 50 K. We have investigated the temperature variation of the Co(2)SiO(4) magnetic structure by means of non-polarized and polarized neutron diffraction for single crystals. Measurements with non-polarized neutrons were made at 2.5 K (below T(N)), whereas polarized neutron diffraction experiments were carried out at 70 and 150 K (above T(N)) in an external magnetic field of 7 T parallel to the b axis. Additional accurate non-polarized powder diffraction studies were performed in a broad temperature range from 5 to 500 K with small temperature increments. Detailed symmetry analysis of the Co(2)SiO(4) magnetic structure shows that it corresponds to the magnetic (Shubnikov) group Pnma, which allows the antiferromagnetic configuration (G(x), C(y), A(z)) for the 4a site with inversion symmetry 1 (Co1 position) and (0,C(y),0) for the 4c site with mirror symmetry m (Co2 position). The temperature dependence of the Co1 and Co2 magnetic moments obtained from neutron diffraction experiments was fitted in a modified molecular-field model. The polarized neutron study of the magnetization induced by an applied field shows a non-negligible amount of magnetic moment on the oxygen positions, indicating a delocalization of the magnetic moment from Co towards neighbouring O owing to superexchange coupling. The relative strength of the exchange interactions is discussed based on the non-polarized and polarized neutron data.

Anomalous thermal expansion of cobalt olivine, Co2SiO4, at low temperatures

“…we have calculated from our measurements that ' 3:1 B . This value corresponds to the high-spin state of Co 2þ (S ¼ 3=2) and is in agreement with neutron diffraction and magnetic susceptibility measurements (Sazonov et al, 2009).…”

“…The solid curves represent a fit (see details in the text). mation on the magnetic properties of Co 2 SiO 4 can be found elsewhere (Sazonov et al, 2009).…”

“…The magnetic structure is quite complex and the magnetic moments and their temperature dependences are different for the M1 and M2 sites. A more detailed description can be found elsewhere (Sazonov et al, 2009).…”

Evolution of two-dimensional antiferromagnetism with temperature and magnetic field in multiferroicBa2CoGe2O7

“…It is estimated to be J = −0.2 K based on a mean field approximation [43]. Based on the parameters obtained from the Curie-Weiss fits, we also calculated the g factor according to [44,45]). …”

Co2SiO4 nanostructures: New simple synthesis, characterization and investigation of optical property

“…One of the less-studied olivine-type silicates is the synthetic Co 2 SiO 4 , cobalt orthosilicate. The Co 2 SiO 4 is a member of the olivine mineral family, has an orthorhombic structure and is widely used as a pigment in the ceramic industry due to its stability at high temperatures and is currently being considered to be used as a magnetic material and as catalyst [10].…”