Since the discovery of the reversible intercalation of lithium-ion materials associated with promising electrochemical properties, lithium-containing materials have attracted attention in the research and development of effective cathode materials for lithium-ion batteries. Despite various studies on synthesis, and electrochemical properties of lithium-based materials, fairly little fundamental optical and thermodynamic studies are available in the literature. Here, we report on the structure, optical, magnetic, and thermodynamic properties of Li-excess disordered rocksalt, Li_1.3Nb_0.3Mn_0.4O₂ (LNMO) which was comprehensively studied using powder X-ray diffraction, transient absorption spectroscopy, magnetic susceptibility, and low-temperature heat capacity measurements. Charge carrier dynamics and electron–phonon coupling in LNMO were studied using ultra-fast laser spectroscopy. Magnetic susceptibility and specific heat data are consistent with the onset of long-range antiferromagnetic order at the Néel temperatures of 6.5 (1.5) K. The effective magnetic moment of LNMO is found to be 3.60 ${\mu }_B$. The temperature dependence of the inverse magnetic susceptibility follows the Curie–Weiss law in the high-temperature region and shows negative values of the Weiss temperature 52 K (3), confirming the strong AFM interactions.

Two Fe(III)Mn(III) bimetallic compounds, [Tp*Fe (CN)₃][(Mn^IIIsalen)]·MeOH·MeCN (1) and [Tp*Fe (CN)₃][Mn^IIIsalphen]·MeOH·H₂O (2), were prepared by assembling the tricyanometalate building block (TEA)₄N [Tp*Fe(CN)₃] [Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate] and the respective Mn Schiff base precursors [salen = N,N'-ethylenebis(salicylideneiminate), salphen = N,N-bis(salicylidene)-1,2-phenylenediamine]. Both compounds exhibit a one-dimensional (1D) zigzag chain structure linked by cyanide bridges, forming a (-Fe-C≡N-Mn-N≡C-) _n motif. Magnetic studies show a gradual increase of χ_M T values in both complexes upon lowering temperature, indicating ferromagnetic coupling between the Fe^III and Mn^III metal centers with Curie-Weiss constants of +1.1 K in (1) and +1.0 K in (2). Ferromagnetic interactions are attributed to the significantly bent Mn-NC angles (148.52 and 152.99° for (1) and 154.9 and 151.3° for (2)). The formation of 1D chains in the presence of MeOH challenges earlier reports that linked chain formation to the absence of MeOH in the reaction medium. This finding highlights the highly sensitive nature of this reaction system to various factors, including the influence of solvents on intermolecular interactions, the coordinative properties and polarity of the solvent, the steric and electronic characteristics of the precursors, and specific reaction conditions, such as temperature, concentration, and molar ratios.

While most studies in disordered rock salt cathode materials focus on synthesis and electrochemical investigation, detailed investigations on their optical and thermodynamic properties are a matter of interest. Here, we report on complementary measurements of transient absorption spectroscopy, thermodynamic, and dielectric properties for Li_1.3Nb_0.3Fe_0.4O₂ (LNFO) disordered rock salt Li-excess. The structure was studied using powder x-ray diffraction and scanning electron microscopy, which showed the fine crystallization of LNFO. The ultra-fast laser spectroscopy is used to study the dynamics of charge carriers and electron–phonon coupling in the system. Our thermodynamic measurements have revealed a magnetically ordered phase with small spontaneous magnetization. The dielectric properties of LNFO illustrate high permittivity with losses at low frequencies. Furthermore, the behavior of the dielectric modulus and AC conductivity vs temperature and frequency were discussed.