Quantum and thermal spin relaxation in diluted spin ice: Dy(2-x)MxTi2O7 (M = Lu, Y)

TL;DR

This study investigates how dilution with non-magnetic ions affects spin relaxation and freezing in Dy-based spin ice, revealing a non-monotonic relaxation behavior and emphasizing local environment effects over spin-spin correlations.

Contribution

It provides new insights into the dilution-dependent spin relaxation dynamics and challenges previous assumptions about spin freezing mechanisms in spin ice materials.

Findings

Spin freezing at ~16 K is suppressed at low dilution but reappears at higher dilution levels.

Quantum spin relaxation time varies non-monotonically with dilution.

Spin freezing is driven by local single-spin processes rather than spin-spin correlations.

Abstract

We have studied the low temperature a.c. magnetic susceptibility of the diluted spin ice compound Dy(2-x)MxTi2O7, where the magnetic Dy ions on the frustrated pyrochlore lattice have been replaced with non-magnetic ions, M = Y or Lu. We examine a broad range of dilutions, 0 <= x <= 1.98, and we find that the T ~ 16 K freezing is suppressed for low levels of dilution but re-emerges for x > 0.4 and persists to x = 1.98. This behavior can be understood as a non-monotonic dependence of the quantum spin relaxation time with dilution. The results suggest that the observed spin freezing is fundamentally a single spin process which is affected by the local environment, rather than the development of spin-spin correlations as earlier data suggested.