Bobby Prevost

Fermi-surface topology of the iron pnictide LaFe2P2

We report on a comprehensive de Haas-van Alphen (dHvA) study of the iron pnictide LaFe2P2. Our extensive density-functional band-structure calculations can well explain the measured angular-dependent dHvA frequencies. As salient feature, we observe only one quasi-two-dimensional Fermi-surface sheet; i.e., a hole-like Fermi-surface cylinder around Γ, essential for s± pairing, is missing. In spite of considerable mass enhancements due to many-body effects, LaFe2P2 shows no superconductivity. This is likely caused by the absence of any nesting between electron and hole bands.

Evidence for SrHo2O4 and SrDy2O4 as model J1-J2 zigzag chain materials

Neutron diffraction and inelastic spectroscopy is used to characterize the magnetic Hamiltonian of SrHo2O4 and SrDy2O4. Through a detailed computation of the crystal-field levels we find site- dependent anisotropic single-ion magnetism in both materials and diffraction measurements show the presence of strong one-dimensional spin correlations. Our measurements indicate that competing interactions of the zig-zag chain, combined with frustrated interchain interactions, play a crucial role in stabilizing spin-liquid type correlations in this series.

Field dependence of the magnetic correlations of the frustrated magnet SrDy2O4

The frustrated magnet SrDy

Absence of long-range order in the frustrated magnet SrDy2O4 due to trapped defects from a dimensionality crossover

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Dimensionality and irreversibility of field-induced transitions in SrDy 2 O 4

O

Coexistence of magnetic fluctuations and long-range order in the one-dimensional J1−J2 zigzag chain materials BaDy2O4 and BaHo2O4

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Absence of long range order in SrDy

exhibits a field-induced phase with a magnetization plateau at

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1/3

O

of the saturation value for magnetic fields applied along the

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b