The temperature dependence of eigenfrequencies and intensities of the IR active modes has been investigated for the antiferromagnetic chromium spinel compounds CdCr2O4, ZnCr2O4, ZnCr2S4, ZnCr2Se4, and HgCr2S4 by IR spectroscopy for temperatures from 5 K to 300 K. At the transition into the magnetically ordered phases, and driven by spin-phonon coupling, most compounds reveal significant splitti...

We report on a Dirac-like Fermi surface in three-dimensional bulk materials in a distorted spinel structure on the basis of density functional theory as well as tight-binding theory. The four examples we provide in this Letter are BiZnSiO4, BiCaSiO4, BiAlInO4, and BiMgSiO4. A necessary characteristic of these structures is that they contain a Bi lattice which forms a hierarchy of chainlike subs...

Magnetization plateaux, visible as anomalies in magnetic susceptibility at low temperatures, are one of the hallmarks of frustrated magnetism. An extremely robust halfmagnetization plateau is observed in the spinel oxides CdCr2O4 and HgCr2O4, where it is accompanied by a substantial lattice distortion. We give an overview of the present state experiment for CdCr2O4 and HgCr2O4, and show how suc...

High voltage spinel LiNi(0.5)Mn(1.5)O(4) is a very promising cathode material for lithium ion batteries that can be used to power hybrid electrical vehicles (HEVs). Through careful control of the cooling rate after high temperature calcination, LiNi(0.5)Mn(1.5)O(4) spinels with different disordered phase and/or Mn(3+) contents have been synthesized. It is revealed that during the slow cooling p...

C. B. Azzoni , M. C. Mozzat i , A. Paleari , M . Bini b , D. Capsoni b , G. Chiodel l i b , and V. Massarot t i b INFM-Department of Physics "A. Volta" of the University, via Bassi 6,1-27100 Pavia a INFM-Department of Materials Science of the University, via Cozzi 53,1-20125 Milano b Department of Physical Chemistry of the University and CSTE-CNR, via Taramelli 16,1-27100 Pavia Reprint requests...

We report a linear dependence of the phonon splitting Δω on the nondominant exchange coupling constant J(nd) in the antiferromagnetic transition-metal monoxides MnO, FeO, CoO, NiO, and in the frustrated antiferromagnetic oxide spinels CdCr(2)O(4), MgCr(2)O(4), and ZnCr(2)O(4). It directly confirms the theoretical prediction of an exchange-induced splitting of the zone-center optical phonon for ...

Batteries that shuttle multivalent ions such as Mg and Ca ions are promising candidates for achieving higher energy density than available with current Li-ion technology. Finding electrode materials that reversibly store and release these multivalent cations is considered a major challenge for enabling such multivalent battery technology. In this paper, we use recent advances in high-throughput...

An equimolar mixtures of starting ZnO and Cr2O3 powders were mechanically activated by grinding using a planetary ball mill for various periods of time (40 to 320 minutes). Formation of nanocrystalline ZnCr2O4 as normal spinel structure at room temperature is detected in all samples after ball-milling. A detailed XRD structural analysis (lattice parameters, site occupancy, the average primary c...