Two different high-entropy oxide materials were synthesized and studied as Li-ion battery anodes. The two materials have the same active metal constituents but different inactive elements which result in different initial crystalline structures: rock salt for (MgFeCoNiZn)O and spinel for (TiFeCoNiZn)${}_3$O${}_4$. Local structural studies of the metal elements in these two materials over extended electrochemical cycling reveal that the redox processes responsible for the electrode capacity are independent of the initial crystallographic structure and that the capacity is solely dependent on the initial random distribution of the metal atoms and the amount of active metals in the starting material.

Oscillatory dynamics is a key tool in optical tweezer applications. It is usually implemented by mechanical interventions that cannot be optically controlled. In this paper, we show that germanium semiconductor beads behave as optically induced oscillators when subjected to a highly focused laser beam. In turn, the well-defined direction of oscillations can be manipulated by the polarization of the light beam. Such unusual motion is due to the competition between the usual optical forces and the radiometric force related to thermal effects, which pushes the beads from the focal region. We characterize the behavior of the germanium beads in detail and propose a model accounting for the related forces in good agreement with the experimental data. Such kind of system can potentially revolutionize the field of optical manipulation, contributing to the design of single molecule machines and to the application of oscillatory forces in fundamental physics, cellular manipulation, fluid dynamics, and other soft-matter systems.

High-entropy oxides (HEOs) are single phase solid solutions where five or more metals share the same sublattice, giving rise to unexpected features in various fields of applications. Recently, HEOs have emerged as an alternative conversion electrode anode material for next-generation Li-ion batteries, where the combination of several different elements in a single solid solution can synergistically act to overcome some of its main drawbacks, improving performance. Due to their chemical complexity, x-ray absorption spectroscopy (XAS) emerges as an appropriate technique to study the electronic (x-ray absorption near edge structure, XANES) and local structure (extended x-ray absorption fine structure, EXAFS) of these compounds as a function of cycling. This work aims to highlight the capabilities of XAS as an element-specific probe to understand a material’s structure at the atomistic level through EXAFS modeling of (MgFeCoNiCuZn)O high-entropy system and how to extract valuable information about the bond distance, number of near neighbors, and local disorder, which are crucial to a full understanding of the electrochemical reaction mechanisms of such battery electrodes.

The magnetic properties of the double perovskites Sm ₂ Mn _{1+ x} Co _{1− x} O ₆ ( x = 0, 0.05, 0.12 and 0.26) were investigated. It was found that the Curie temperature, the lattice parameters and the net magnetic moments increased for increasing amounts of Co. An irreversible behavior was observed by measuring the magnetization after cooling the sample with and without applied magnetic fields ( H ). The temperature below which the irreversibility was observed is H dependent and the data were nicely fit to de Almeida–Thouless lines. The ac magnetic susceptibility was measured for frequencies f in the range 0.03–10 kHz yielding for the shifting in the freezing temperature per decade of f . The spin-dynamics were found to follow a power-law with a product of the critical exponents of about 4.99. The overall results are understood within a framework where the variation in the bonding angle associated to the super-exchange interactions are taken into consideration.