Melting of Spin Ice state through structural disorder in Dy2Zr2O7

TL;DR

This study investigates how structural disorder in Dy2Zr2O7 disrupts the spin ice state, revealing persistent spin dynamics and absence of residual entropy, contrasting with ordered Dy2Ti2O7.

Contribution

It demonstrates that structural disorder melts the spin ice state, leading to a dynamic, liquid-like magnetic state without spin freezing.

Findings

Antiferromagnetic correlations develop below 10 K.

No residual entropy observed at low temperatures.

Disorder prevents spin freezing, maintaining dynamic spins.

Abstract

Neutron scattering, a.c. magnetic susceptibility and specific heat studies have been carried out on polycrystalline Dy2Zr2O7. Unlike the pyrochlore spin ice Dy2Ti2O7, Dy2Zr2O7 crystallizes into the fluorite structure and the magnetic Dy3+ moments randomly reside on the corner-sharing tetrahedral sublattice with non-magnetic Zr ions. Antiferromagnetic spin correlations develop below 10 K but remain dynamic down to 40 mK. These correlations extend over the length of two tetrahedra edges and grow to 6 nearest neighbors with the application of a 20 kOe magnetic field. No Pauling's residual entropy was observed and by 8 K the full entropy expected for a two level system is released. We propose that the disorder melts the spin ice state seen in the chemically ordered Dy2Ti2O7 compound, but the spins remain dynamic in a disordered, liquid-like state and do not freeze into a glass-like state that one might intuitively expect.