Electrochemical Tuning-Induced Magnetic Transitions in Geometrically Frustrated Spinel LixMn2O4 (0.07 ≤ x ≤ 0.93)

Precise tuning of the magnetic states of geometrically frustrated materials remains a critical challenge, as this process will not only promote understanding of fundamental magnetism but also accelerate the discovery of new materials with unprecedented magnetic behaviors. In this article, we present a study of the tuning magnetic properties of spinel LiMn2O4 by electrochemical oxidation/reduction in a lithium battery. The ex-situ magnetic susceptibility and specific heat measurements were performed on electrochemically modified LixMn2O4 with 0.07 <= x <= 0.93 to monitor the evolution of magnetic phase transitions and identify the new magnetic intermediate state. The results showed that the strong frustrated Li0.93Mn2O4 is in a spin-glass ground state, while the weak frustrated Li0.07Mn2O4 (or lambda-MnO2) exhibits long-range antiferromagnetic order. In addition, a unique magnetic ground state of noncollinear antiferromagnetic order was found in the intermediate phase Li0.50Mn2O4 below 16 K, which was unveiled for the first time in the spinel LixMn2O4 system. The results of our work suggest that the nontrivial magnetic order may arise from the symmetry-broken spin states in a geometrically frustrated lattice and could be easily achieved by an electrochemical method but more difficult to prepare via traditional chemical methods.