Microscopic magnetic and structural nature of spinelLi[LixMn2−x]O4

Abstract

The magnetic nature of the spinel antiferromagnet Li͓Li x Mn 2−x ͔O 4 with x = 0 -0.15 has been studied with muon-spin rotation and relaxation ͑ + SR͒ spectroscopy. Both weak-transverse-field and zero-field + SR measurements indicate that the whole sample enters into a static disordered magnetic phase below T N for all the samples measured; T N = 61 K for LiMn 2 O 4 , but 27-23 K for the x = 0.05-0.15 samples. It was also clarified that both the field distribution width and the field fluctuation rate show a clear change at the Jahn-Teller ͑JT͒ transition temperature ͑T JT = 280 K͒ for LiMn 2 O 4 , and a short-range cooperative JT distortion appears below 280 K even for Li͓Li 0.15 Mn 1.85 ͔O 4 .

Magnetic excitations in the spinel compoundLix[Mn1.96Li0.04]Heitmann1, Schmets2, Gaddy3 et al. 2010Phys. Rev. B9040View full textAdd to dashboardCite

“…That is, all curves coincide to such an extent that E / T-scaling behavior seems to take place. Even at the lowest temperature ͑T = 24 K, close to the temperature where the superspins are starting to freeze out 35,36,38,39 ͒ and at the highest temperature ͑T = 100 K, above the temperature where the Mn 4+ ions in the clusters have fully lined up͒, the line shape of the response is still remarkably similar to the data taken at T =33 and 41 K.…”

“…This makes this family of compounds an ideal testbed for investigating whether quantum critical scaling laws [12][13][14][15]26 could, in fact, be associated with cluster formation in such systems. After all, Li x ͓Mn 1.96 Li 0.04 ͔O 4 is a purely classical system ͑from a phase transition point of view 36 ͒ that is disordered because of geometric frustration and Li/Mn disorder; clusters of AF-aligned Mn 4+ ions ͑superspins͒ are present below ϳ70 K. 29 The fact that the system's phase transition is classical follows from neutron-scattering results that show the cluster dynamics freezing out ϳ20-25 K for all values of x, and from susceptibility measurements 39 that show a phase transition around ϳ20-25 K for all x. Insulating Li x ͓Mn 1.96 Li 0.04 ͔O 4 should not exhibit any type of quantum critical scaling as observed in metallic quantum critical systems, 9 however, next we argue that its response shows all the hallmarks of E / T scaling; hallmarks that were thought to be associated exclusively with quantum criticality. We argue, without using any particular line-shape analysis, that scattering originating from the superspins effectively mimics quantum scaling behavior and that this scaling can be observed even in the compound that displays long-range ordering ͑x = 0.2͒.…”

“…This suppression of the structural transition near room temperature is a boon to the battery industry as it prevents the degradation of the material during recharging cycles of the battery. 30 Neutron-scattering studies 34 and muon investigations 35,36 on the doped material have shown that long-range magnetic order is destroyed for y Ͼ 0.02 and and 11͒ where ordering is established through a spin-density wave instability of the Fermi surface. ͑b͒ The local moment scenario ͑Refs.…”

“…x Ͼ 0.3, and that the material appears to enter a spin glass phase around 15-25 K ͑with the transition temperature dependent upon the exact Li content 36 ͒. For the compound with y = 0.04, long-range magnetic order is re-established below ϳ35 K when the A sites are heavily depleted ͑x = 0.2͒.…”

Observation of Li Diffusion in Cathode Sheets of Li-ion Battery by μ+SR

“…Furthermore, since the initial muon spin is 100% polarized, the contribution of magnetic ions is distinguishable from that of nuclear moments by applying a weak longitudinal field, typically below 10 Oe. This is a significant advantage over Li-NMR, particularly for measuring D Li in cathode materials, such as, LiCoO 2 [1], LiNiO 2 [2], LiMn 2 O 4 [3], and LiFePO 4 [4]. Moreover, the range of the implanted muons is tunable by adjusting the implantation energy.…”