Quantum matter in high magnetic fields

Abstract:

We report millimeter-wave magneto-optical measurements on the high-spin molecule, Cr10 (OMe) 20 (O2 CCMe3) 10. The dependence of the electron paramagnetic resonance as a function of orientation and temperature demonstrates that this compound behaves as a single molecule magnet, and exhibits one of the smallest zero-field splittings (D=-0.045±0.004 K) yet reported for such a system. © 2005 American Institute of Physics.

Abstract:

We report high-field magnetotransport measurements on β″-(BEDT- TTF)4[(H3O)M(C2O4) 3]· solvent, where M=Ga³⁺, Cr³⁺ and Fe³⁺ and solvent=C5H5N. In spite of their differing transition metal-ions, M, the three compounds exhibit similar magnetic quantum oscillation spectra superimposed on a positive magnetoresistance. At least four independent quantum oscillation frequencies have been identified, corresponding to two different hole and electron pockets of the Fermi surface which follow the rules of a compensated metal. Observation of the small pockets could be the result of the Fermi surface reconstruction induced by a possible density wave. The effective masses are very similar for different samples and for different pockets range between meff ≈ 0.5-1.1 me whereas the Dingle temperatures varies between TD ≈ 1.4-4 K. At low temperature, the longitudinal magnetoresistance violates Kohler's rule, suggesting that the interlayer transport in these quasi-2D systems cannot be related to a single scattering time and that the disorder plays an important role. © EDP Sciences.

Abstract:

We report magnetotransport measurements performed in magnetic fields of up to 33 T and at low temperatures (0.45 K4[(H3O)M(C2O4)3]· C6H5NO2, where the 3d metal ion M is either non-magnetic Ga³⁺ or magnetic Cr³⁺, Quantum oscillations suggest that the salt with M = Ga has two two-dimensional Fermi surface pockets (45 T and 230 T) whereas when M = Cr only one pocket (230 T) is observed. Replacing Ga with Cr has the effect of enhancing the effective mass of the 230 T pocket from 1.2 ± 0.2 me to 2.2 ± 0,3 me and reducing the superconducting critical temperature from Tc ≈ 8 K to Tc ≈ 5 K. © EDP Sciences.