Muons and magnets

Abstract:

Magnetic materials in which the fundamental building block is molecular have attracted a great deal of interest because they capitalize on the flexibility inherent in carbon chemistry. Some compounds incorporating chemically stable free radicals are purely organic and show long-range magnetic order at very low temperatures, but the most useful molecular magnets incorporate transition metal or lanthanide ions, with the molecular groups providing a bridge to mediate exchange interactions between the ions. Some of these materials exhibit a spin crossover effect between low-spin and high-spin states. Other molecular magnets form model low-dimensional magnetic compounds that can be used to test models of quantum spin systems. Molecular nanomagnets are complex molecules containing a number of metal ions whose individual moments conspire to create a giant magnetic moment associated with the entire molecule. These systems can be used to exhibit quantum tunnelling of magnetization and are also candidate systems for quantum computing applications.

Abstract:

We present experimental evidence for a hitherto unconfirmed type of angle-dependent magnetoresistance oscillation caused by magnetic breakdown. The effect was observed in the organic superconductor κ- (BEDT-TTF)2 Cu (NCS)2 using hydrostatic pressures of up to 9.8 kbar and magnetic fields of up to 33 T. In addition, we show that similar oscillations are revealed in ambient-pressure measurements, provided that the Shubnikov-de Haas oscillations are suppressed either by elevated temperatures or filtering of the data. These results provide a compelling validation of Pippard's semiclassical picture of magnetic breakdown. © 2007 The American Physical Society.

Abstract:

We present a detailed muon spin relaxation (μ+SR) study of the spin-ice material Dy2Ti2O7. Polycrystalline samples of this material have been studied in the temperature range 0.02K

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