Distinguishing the Intrinsic Antiferromagnetism in Polycrystalline LiCoPO₄and LiMnPO₄Olivines

Abstract

We report a detailed investigation of the long-range magnetic ordering in polycrystalline samples of LiCoPO4 and LiMnPO4, which belong to a series of well-known olivine cathode materials LiMPO4 (M = Mn, Fe, Co, Ni). Samples were prepared by hydrothermal and solid state methods. The magnetic susceptibility is found to be strongly field-dependent, impacting the antiferromagnetic transition temperature and the bifurcation of the FC and ZFC curves. We discuss the role synthesis conditions have on impurity formation and particle size. We report neutron powder diffraction data for the samples prepared by solid state methods. Based upon representational analysis of the observed reflections, we affirm the magnetic structure Pnma′ for LiCoPO4 and Pn′m′a′ for LiMnPO4. The refined magnetic moments from these models are 3.28(4) μB for LiCoPO4 and 4.28(3) μB for LiMnPO4. We also study the onset of magnetic ordering in each sample and affirm that the ordering temperature is 22 K for LiCoPO4 and 34 K for LiMnPO4. The critical parameters describing those transitions are βc = 0.21(4) (LiCoPO4) and βc = 0.31(3) (LiMnPO4). These values are characteristic of a 3D Ising system for LiMnPO4 and intermediate behavior between a 2D and 3D Ising system for LiCoPO4. We compare these observations with other reports proposing lower magnetic symmetry.

Tuning Magnetic Symmetry and Properties in the Olivine Series Li1–xFexMn1–xPO4 through Selective Delithiation

“…These moments then move closer and closer to the M x and M y of FePO 4 (Table ). While every delithiated sample’s total magnetic moment falls short of the expected 5 μ B , this is consistent with past reports on olivines. , …”

“…Rousse et al reported the FePO 4 refined magnetic moment to be 4.15 μ B , while the expected is 5 μ B . Gnewuch and Rodriguez found a total moment of 4.28(3) μ B in LiMnPO 4 , while the expected moment is also 5 μ B …”

Accelerated Development of High Voltage Li‐Ion Cathodes

“…The magnetic ordering preference of LCP was calculated to demonstrate the intrinsic antiferromagnetism in LCP. [33] The activation barriers of Li migration were calculated using the CI-NEB method. [34,35] All the lattice parameters were fixed, but all the atomic positions were relaxed within the supercell during the CI-NEB calculations.…”

Magnetic structure and properties of a vanthoffite mineral Na6Mn(SO4)4

“…Specifically, the compound T bP O 4 [26,27] displays intrinsic bulk magneto-electric effect. A series of polyanionic phosphates LiM P O 4 (M = Mn, Co, Ni or Fe) have aroused special interest to evaluate the associated magnetic behaviour in these minerals [19,[28][29][30][31][32].…”