# Epsilon-iron as a spin-smectic state

## TL;DR

This paper identifies a novel spin-smectic magnetic state in high-pressure iron, combining experimental spectroscopy and first-principles calculations, which explains the absence of magnetic order and may relate to superconductivity.

## Contribution

It introduces the concept of a spin-smectic state in high-pressure iron, providing a new theoretical and experimental understanding of its magnetic properties.

## Key findings

- Local magnetic moments persist up to 30-40 GPa
- No magnetic order detected down to 1.8 K
- First-principles calculations reveal a spin-smectic state

## Abstract

Using x-ray emission spectroscopy, we find appreciable local magnetic moments until 30-40 GPa in the high-pressure phase of iron, however no magnetic order is detected with neutron powder diffraction down to 1.8 K contrary to previous predictions. Our first-principles calculations reveal a "spin-smectic" state lower in energy than previous results. This state forms antiferromagnetic bilayers separated by null spin bilayers, which allows a complete relaxation of the inherent frustration of antiferromagnetism on a hexagonal close-packed lattice. The magnetic bilayers are likely orientationally disordered, owing to the soft interlayer excitations and the near-degeneracy with other smectic phases. This possible lack of long-range correlation agrees with the null results from neutron powder diffraction. An orientationally-disordered, spin-smectic state resolves previously perceived contradictions in high pressure iron and could be integral to explaining its puzzling superconductivity.