A toroidal moment occurs when magnetic moments align in a way that produces a moment normal to those magnetic moments. When these toroidal moments spontaneously align at a specific temperature, the resulting phenomena is called ferrotoroidicity. To achieve ferrotoroidicity, specific orientations of the magnetic moments, and therefore specific magnetic point groups are allowed. LiFePO4 has a magnetic point group of m’mm (allowed) and it’s delithiated form, FePO4, has a point group of 222 (not allowed). Our specific aim is to study the magnetic properties of the partially delithiated Li1-xFexMn1-xPO4 series. The goal of this research is to maximize the transition temperature, while maintaining an allowed magnetic space group. This ideal material would have potential applications in data processing speeds, data storage, energy consumption and more. We successfully synthesized the phase pure powder samples of LiFexMn1-xPO4 using a solid-state method and grew single crystals using a salt-flux method. These materials have also been selectively delithiated using an oxidizing peracetic acid solution. Powder x-ray diffraction (pXRD) data confirmed that the materials crystallize in a Pnma structure and are phase pure. Temperature dependent magnetic susceptibility measurements have shown that that the partially delithiated structures have higher transition temperatures than those that are lithiated. While the Pnma structure is always maintained, after a certain amount of lithium is removed, the magnetic point group changes to one that does not support ferrotoroidicity. We can use the pXRD, susceptibility, and neutron powder diffraction data, to solve the magnetic structure of these partially delithiated materials. The structure that maximizes the transition temperature while retaining the m’mm magnetic point group can then be determined.

Structural and magnetic analysis of partially delithiated transition metal phosphates

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.