Oren Ofer

Nature of weak magnetism in SrTiO3/LaAlO3 multilayers.

We report the observation of weak magnetism in superlattices of LaAlO(3)/SrTiO(3) using β-detected nuclear magnetic resonance. The spin lattice relaxation rate of ^{8}Li in superlattices with a spacer layers of 8 and 6 unit cells of LaAlO(3) exhibits a strong peak near ~35 K, whereas no such peak is observed in a superlattice with spacer layer thickness of 3 unit cells. We attribute the observed temperature dependence to slowing down of weakly coupled electronic moments at the LaAlO(3)/SrTiO(3) interface. These results show that the magnetism at the interface depends strongly on the thickness of the spacer layer, and that a minimal thickness of ~4-6 unit cells is required for the appearance of magnetism. A simple model is used to determine that the observed relaxation is due to small fluctuating moments (~0.002μ(B)) in the two samples with a larger LaAlO(3) spacer thickness.

Strain, spin disorder, and thickness dependence of magneto-transport in Sm0.55Sr0.45MnO3 films

The correlation between the strain, spin disorder, and the thickness dependence of the magneto-transport has been investigated in as-grown and post-annealed 25-300-nm thick films of Sm0.55Sr0.45MnO3 (SSMO) deposited on SrTiO3 (STO) and LaAlO3 (LAO) substrates. In the post-annealed SSMO/LAO films, the epitaxial strain increases with a decreasing thickness; however, it is independent of the thickness of the post-annealed SSMO/STO films. In both cases, the reduction of the metal-insulator transition temperature with a decreasing thickness was observed. This behavior is attributed to an increasing compressive strain in the SSMO/LAO films and to spin disorder effects in the SSMO/STO ones.

The magnetic structure of the zigzag chain family Na

We present muon-spin-rotation measurements on polycrystalline samples of the complete family of the antiferromagnetic AF zigzag chain compounds, NaxCa1�xV2O4. In this family, we explore the magnetic properties from the metallic NaV2O4 to the insulating CaV2O4. We find a critical xc0.833 which separates the low and high Na-concentration-dependent transition temperature and its magnetic ground state. In the xxc compounds, the magnetic ordered phase is characterized by a single homogenous phase and the formation of incommensurate spin-density-wave order. Whereas in the xxc compounds, multiple subphases appear with temperature and x. Based on the muon data obtained in zero external magnetic field, a careful dipolar field simulation was able to reproduce the muon behavior and indicates a modulated helical incommensurate spin structure of the metallic AF phase. The incommensurate modulation period obtained by the simulation agrees with that determined by neutron diffraction.

_{x}

We present magnetization measurements on oriented powder of ZnCu

Ca

_{3}

_{1-x}

(OH)

V

_{6}

_2

Cl

O

_{2}

_4

along and perpendicular to the orienting field. We find a dramatic difference in the magnetization between the two directions. It is biggest at low measurement fields