Magnetic structures of βI-Li2CoSiO4 and γ0-Li2MnSiO4: Crystal structure type vs. magnetic topology

•Magnetic structures of Li2CoSiO4 and Li2MnSiO4 were studied for the first time.•Both materials antiferromagnetically order around 12–14 K.•Despite different crystal structure magnetic structures are of the same type.•The fact is attributed to similar topology of magnetic interactions.

The magnetic structure and properties of the candidate lithium-ion battery cathode materials Pbn21(≡Pna21) Li2CoSiO4 and P21/n Li2MnSiO4 have been studied experimentally using low-temperature neutron powder diffraction and magnetometry. Both materials undergo long-range antiferromagnetic ordering, at 14 K and 12 K respectively, due to super–super-exchange mediated by bridging silicate groups. Despite having different crystal structures (wurtzite- vs. “dipolar”-type), Li2CoSiO4 and Li2MnSiO4 have the same topology in terms of magnetic interactions, and adopt collinear magnetic structures of the same type with the propagation vectors (0, 1/2, 1/2) and (1/2, 0, 1/2), respectively. The magnetic moments in the two materials are aligned in parallel and obliquely to the distorted closed-packed layers of oxygen atoms. The experimentally observed values of the ordered magnetic moments, 2.9 μB and 4.6 μB, are close to those expected for d7 Co2+ and d5 Mn2+, respectively.

Graphical abstractDespite the different crystal structures βI-Li2CoSiO4 and γ0-Li2MnSiO4 have similar magnetic topology and as a result adopt magnetic structure of the same type.Figure optionsDownload full-size imageDownload as PowerPoint slide