Résumé
Polarised positive muons can be implanted into any type of material and rapidly thermalize, then the local magnetic environment dictates the evolution of muon spin vectors and provokes the muon depolarisation. The muon spin relaxation (μSR) technique provides interesting information on magnetism and spin dynamics in spinel lithium manganates insertion compounds. In this work, we compare the behaviour of muons into a lithium-rich spinel manganese oxide and its lithium extracted product. The chemical extraction of lithium from Li
1.33Mn
1.67O
4, where all the manganese is Mn
IV, is essentially a lithium by proton ion exchange process to give a protonated manganese oxide with spinel structure, H
+–MnO
2. Muons clearly have showed the presence of protons in H
+–MnO
2, and the movement of lithium ions or protons at increasing temperatures in both samples. Muons are quasi-static in these compounds, and they are located both in ‘regular’ lithium and proton sites and also in interstitial sites of the spinel structure, these latter being used during diffusion of lithium ions. Below 50 K, static muons behave as in a paramagnet, where Mn magnetic spins are slowing down and ordering near 6 and 14 K in the protonated and lithiated spinels, respectively.