From Cooperative Paramagnet to N\'{e}el Order in Y_2Ru_2O_7

TL;DR

This study investigates the evolution of spin correlations in Y_2Ru_2O_7 from a cooperative paramagnet to an ordered Ne9el state using neutron scattering, revealing temperature-dependent spectral features and spin dynamics.

Contribution

It provides detailed neutron scattering data showing how spin correlations evolve across the magnetic transition in Y_2Ru_2O_7, highlighting the change from relaxation to gapped excitations.

Findings

Spin relaxation rate scales with temperature as 7(9)k_B T.

Spectral weight shifts to higher energies below T_N.

An energy gap of 11 meV appears at low temperatures.

Abstract

Spin correlations in the pyrochlore antiferromagnet Y_2Ru_2O_7 with Curie-Weiss temperature $\Theta_{CW}=-1100$ K and critical temperature T_N=77 K were examined through neutron scattering. For $T_N<T<\Theta_{CW}/3$ the data show spin relaxation with a rate $\hbar\Gamma= 1.17(9)k_BT$. For T<T_N spectral weight moves to higher energies with substantial changes up to $4\times k_BT_N$. For T<<T_N there is a $\Delta=11(1)$ meV energy gap and a pronounced spectral maximum at 19.7 meV. Throughout the temperature range examined the wave vector dependence of inelastic scattering exhibits a broad peak for $Qd\approx 3.8$ (d is Ru-Ru spacing) consistent with dipolar spin correlations.