Muons and magnets

Abstract:

We present a first-principles investigation of the spin-ice state in Dy2Ti2O7 using a magnetic source-free exchange and correlation (xc) functional, implemented in the Castep electronic-structure code. By comparing results from the conventional local spin-density approximation, we show that a spin-ice state in Dy2Ti2O7 can be reliably obtained by removing the magnetic sources from the xc contributions to the potential, and we contrast this against the computed ground states of other frustrated pyrochlore magnets.

Abstract:

Y-kapellasite [ ${\mathrm{Y}}_3{\mathrm{Cu}}_9{(\mathrm{OH})}_{19}{\mathrm{Cl}}_8$ ], which hosts an original anisotropic kagome sublattice, is a promising candidate for studying elusive and complex correlated physics. It exhibits a theoretically predicted in-plane $(1/3,1/3)$ magnetic order [Hering , ], but its magnetic interaction values place it close to a phase boundary to a spin liquid state [Chatterjee , ]. Our $\mathrm{\mu }\mathrm{SR}$ measurements under hydrostatic pressure demonstrate the complete suppression of static magnetism in favor of a fully dynamical ground state at 2.3 GPa. Complementary high-pressure x-ray and optical phonon measurements reveal a gradual reduction of the kagome anisotropy, enhancing magnetic frustration without structural transitions. Our results establish Y-kapellasite as a rare clean kagome model in which long-range order is suppressed by pressure-tuned frustration, the first fingerprint for the realization of a quantum spin liquid without strong disorder.

Abstract:

Hydrogels containing C=O groups and calcium cations show an unexpected paramagnetic effect that may have biomedical applications.