Gavin Lawes

Dielectric anomalies and spiral magnetic order in CoCr2O4

We have investigated the structural, magnetic, thermodynamic, and dielectric properties of polycrystalline CoCr2O4, an insulating spinel exhibiting both ferrimagnetic and spiral magnetic structures. Below Tc=94 K the sample develops long-range ferrimagnetic order, and we attribute a sharp phase transition at TS27 K to the onset of long-range spiral magnetic order. Neutron measurements confirm that the structure remains cubic at 80 K and at 11 K; the magnetic ordering by 11 K is seen to be rather complex. Density functional theory supports the view of a ferrimagnetic semiconductor with magnetic interactions consistent with noncollinear ordering. Capacitance measurements on CoCr2O4 show a sharp decrease in the dielectric constant at TS, but also an anomaly showing thermal hysteresis falling between approximately T=50 and 57 K. We tentatively attribute the appearance of this higher-temperature dielectric anomaly to the development of short-range spiral magnetic order, and discuss these results in the context of utilizing dielectric spectroscopy to investigate noncollinear short-range magnetic structures.

Magnetodielectric coupling in Mn3O4

We have investigated the dielectric anomalies associated with spin-ordering transitions in the tetragonal spinel

Ferromagnetism and spin-polarized charge carriers in In2 O3 thin films

{\mathrm{Mn}}_{3}{\mathrm{O}}_{4}

Control of phase in phosphide nanoparticles produced by metal nanoparticle transformation: Fe2P and FeP.

using thermodynamic, magnetic, and dielectric measurements. We find that two of the three magnetic ordering transitions in

Weak ferromagnetic ordering in Ca doped polycrystalline BiFeO3

{\mathrm{Mn}}_{3}{\mathrm{O}}_{4}

Inorganic–organic multiferroic hybrid films of Fe3O4 and PVDF with significant magneto-dielectric coupling

lead to decreases in the temperature-dependent dielectric constant at zero applied field. Applying a magnetic field to the polycrystalline sample leaves these two dielectric anomalies practically unchanged, but leads to an increase in the dielectric constant at the intermediate spin-ordering transition. We discuss possible origins for this magnetodielectric behavior in terms of spin-phonon coupling. Band structure calculations suggest that in its ferrimagnetic state,

Undoped vacuum annealed In2O3 thin films as a transparent conducting oxide

{\mathrm{Mn}}_{3}{\mathrm{O}}_{4}

Raman scattering studies of magnetic Co-doped ZnO thin films

corresponds to a semiconductor with no orbital degeneracy due to strong Jahn-Teller distortion.

Complex magnetic order in the kagomé staircase compound Co3V2O8

We present evidence for spin-polarized charge carriers in

Oxygen vacancy enhanced room temperature magnetism in Al-doped MgO nanoparticles

{\text{In}}_{2}{\text{O}}_{3}