# Field dependence of the magnetic correlations of the frustrated magnet SrDy$_2$O$_4$

## TL;DR

This study investigates the magnetic correlations in SrDy$_2$O$_4$, revealing a field-induced phase with long-range order consistent with the ANNNI model, contrasting with zero-field short-range order.

## Contribution

It provides the first neutron scattering analysis of the magnetic order in SrDy$_2$O$_4$'s field-induced phase, linking it to the ANNNI model and highlighting the role of quantum fluctuations.

## Key findings

- Long-range magnetic order appears in the field-induced phase.
- Order matches the one-dimensional ANNNI model predictions.
- Zero-field state exhibits short-range magnetic correlations.

## Abstract

The frustrated magnet SrDy$_2$O$_4$ exhibits a field-induced phase with a magnetization plateau at $1/3$ of the saturation value for magnetic fields applied along the $b$-axis. We report here a neutron scattering study of the nature and symmetry of the magnetic order in this field-induced phase. Below $T\approx 0.5$ K, there are strong hysteretic effects, and the order is short or long ranged for zero-field and field cooling, respectively. We find that the long-range ordered magnetic structure within the zig-zag chains is identical to that expected for the one-dimensional axial next-nearest neighbour Ising (ANNNI) model in longitudinal field. The long-range ordered structure in field contrasts with the short-range order found at zero field, and is probably reached through enhanced quantum fluctuations with increasing fields.