Pressure dependence of magnetic transition temperature in Li[LixMn2-x]O4 (0 ≤ x ≤ 1/3) studied by muon-spin rotation and relaxation

In order to study a change in electrochemical, structural, and magnetic properties for lithium manganese oxide spinels Li[LixMn2-x]O-4 (LMO) with 0 <= x <= 1/3, muon-spin rotation and relaxation (mu SR) spectra were recorded under pressure (P) up to 2.1 GPa. At ambient P, P = 0.1 MPa, the antiferromagnetic or spin-glass-like transition temperature (T-m) at P = 0.1 MPa monotonically decreases with increasing x. On the contrary, the slope of the T-m vs. P (dT(m)/dP) rapidly increases from 0.9(1) K/GPa at x = 0 to 1.4 K/GPa at x = 0.1, then drops to 0.7(1) K/GPa at x = 0.15, and finally keeps constant (similar to 0.4 K/GPa) with further increasing x. Considering the structural change of LMO with x, the decrease in the distance between Mn ions (d(Mn-Mn)) is likely to play an essential role for determining T-m under P. According to cyclic voltammetry on LMO, the peak current at both anodic and cathodic directions shows the maximum at x = 0.1, indicating the highest diffusivity of Li+ ions (D-Li) at x = 0.1. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4790377]