A. M. Hallas

Liquidlike Correlations in Single-Crystalline Y2Mo2O7: An Unconventional Spin Glass

The spin glass behavior of Y2Mo2O7 has puzzled physicists for nearly three decades. Free of bulk disorder within the resolution of powder diffraction methods, it is thought that this material is a rare realization of a spin glass resulting from weak disorder such as bond disorder or local lattice distortions. Here, we report on the single crystal growth of Y2Mo2O7. Using neutron scattering, we present unique isotropic magnetic diffuse scattering arising beneath the spin glass transition despite having a well-ordered structure at the bulk level. Despite our attempts to model the diffuse scattering using a computationally exhaustive search of a class of simple spin Hamiltonians, we were unable to replicate the experimentally observed energy-integrated (diffuse) neutron scattering. A T^2-temperature dependence in the heat capacity and density functional theory calculations hint at significant frozen degeneracy in both the spin and orbital degrees of freedom resulting from spin-orbital coupling (Kugel-Khomskii type) and random fluctuations in the Mo environment at the local level.

Magnetic frustration in lead pyrochlores

The rich phase diagrams of magnetically frustrated pyrochlores have maintained a high level of interest over the past 20 years. To experimentally explore these phase diagrams requires a means of tuning the relevant interactions. One approach to achieve this is chemical pressure, that is, varying the size of the nonmagnetic cation. Here, we report on the family of lead-based pyrochlores

Experimental Insights into Ground-State Selection of Quantum XY Pyrochlores

{A}_{2}{\text{Pb}}_{2}{\text{O}}_{7}

Effect of interlayer coupling on the coexistence of antiferromagnetism and superconductivity in Fe pnictide superconductors: A study of Ca 0.74 ( 1 ) La 0.26 ( 1 ) ( Fe 1 − x Co x ) As 2 single crystals

(

Volume-wise destruction of the antiferromagnetic Mott insulating state through quantum tuning

A

Cubic Re6+ (5d1) Double Perovskites, Ba2MgReO6, Ba2ZnReO6, and Ba2Y2/3ReO6: Magnetism, Heat Capacity, μSR, and Neutron Scattering Studies and Comparison with Theory

= Pr, Nd, Gd), which we have characterized with magnetic susceptibility and specific heat. Lead is the largest known possible

μSR study of the noncentrosymmetric superconductor PbTaSe2

B

XY antiferromagnetic ground state in the effective S = 1 2 pyrochlore Yb 2 Ge 2 O 7

-site cation for the pyrochlore lattice. Thus, these materials significantly expand the phase space of the frustrated pyrochlores.

Antiferromagnetism and hidden order in isoelectronic doping of URu2Si2

{\text{Pr}}_{2}{\text{Pb}}_{2}{\text{O}}_{7}

Magnetic dilution and domain selection in the X Y pyrochlore antiferromagnet Er 2 Ti 2 O 7

has an absence of long-range magnetic order down to 400 mK and a spin-ice-like heat capacity anomaly at 1.2 K. Thus,