A study of spin canting in Li3Fe2(PO4)3 with Mössbauer spectroscopy under 5 T

Abstract

Li3Fe2(PO4)3 has been actively studied as a Lithium ion battery cathode material for the next-generation energy storage application. Here, we have investigated the changes of magnetic coupling between two different magnetic sub-lattices in Li3Fe2(PO4)3 with x-ray diffraction (XRD), superconducting quantum interference device (SQUID), and Mössbauer spectroscopy measurements. The experimental XRD pattern was analyzed using Rietveld refinement, confirming single phase. In order to investigate the magnetic property, the SQUID measurement under applied field of 5 T was performed between 4.2 and 295 K. From the temperature-dependent zero-field-cooled and field-cooled magnetization curves, we observed the magnetization decreasing with increasing temperature up to Tmin = 13 K, at which the magnetization showed a minimum value. With continuing increase in temperature, the magnetization starts increasing with a maximum value at Tmax = 28 K and beyond Tmax, the magnetization decreases with the further increase in temperature. Based on the experimentally measured Mössbauer spectra, we identified that the ratios of first and sixth to second and fifth absorption lines were identical around Tmin, while with increasing temperature the area of second and fifth absorption line rapidly decreased up to Tmax. Our study suggests that the spin canting angle between the applied field and hyperfine field of Li3Fe2(PO4)3 is constant up to Tmin. However, the spin canting angle starts decreasing with increasing temperature, reaching a minimum value at Tmax, and beyond Tmax it is increasing. We expect that around Tmax, the ferrimagnetically coupled spin arrangement is appeared to be collinear along the applied field direction under applied field of 5 T.