Biomedical subjects

Carsten Timm

Publications and source records attributed to Carsten Timm.

3 recordsLinked to original sources

PubMed2006

Charge and magnetization inhomogeneities in diluted magnetic semiconductors.

It is predicted that III-V diluted magnetic semiconductors can exhibit stripelike modulations of magnetization and carrier concentration. This inhomogeneity results from the strong dependence of the magnetization on the carrier concentration. Within Landau theory, a characteristic temperature T* below the Curie temperature is found so that below T* the equilibrium magnetization shows modulations, which are strongly anharmonic. The wavelength and amplitude of the modulation rise for decreasing temperature, starting from zero at T*. Above T*, the equilibrium state is homogeneous, but the coupling between charge and magnetization leads to the appearance of an electrically charged layer in domain walls.

Journal Article↗

PubMed2005

Disorder-induced resistive anomaly near ferromagnetic phase transitions.

We show that the resistivity rho(T) of disordered ferromagnets near, and above, the Curie temperature T(c) generically exhibits a stronger anomaly than the scaling-based Fisher-Langer prediction. Treating transport beyond the Boltzmann description, we find that within mean-field theory, drho/dT exhibits a |T - T(c)|(-1/2) singularity near T(c). Our results, being solely due to impurities, are relevant to ferromagnets with low T(c), such as SrRuO(3) or diluted magnetic semiconductors, whose mobility near T(c) is limited by disorder.

Journal Article↗

PubMed2002

Liquid antiferromagnets in two dimensions.

It is shown that, for proper symmetry of the parent lattice, antiferromagnetic order can survive in two-dimensional liquid crystals and even isotropic liquids of pointlike particles, in contradiction to what common sense might suggest. We discuss the requirements for antiferromagnetic order in the absence of translational and/or orientational lattice order. One example is the honeycomb lattice, which upon melting can form a liquid crystal with quasi-long-range orientational and antiferromagnetic order but short-range translational order. The critical properties of such systems are discussed. Finally, we draw conjectures for the three-dimensional case.

Journal Article↗