# Magnetic competition induced colossal magnetoresistance in n-type HgCr2Se4 under high pressures

## TL;DR

This study reveals that high pressure and magnetic fields induce colossal magnetoresistance in n-type HgCr2Se4 by tuning its magnetic state between ferromagnetic and antiferromagnetic phases, highlighting a critical balance of magnetic interactions.

## Contribution

It demonstrates pressure and magnetic field control over magnetic states and colossal magnetoresistance in n-type HgCr2Se4, a single-valent system, revealing a new platform for CMR phenomena.

## Key findings

- High pressure destabilizes ferromagnetic metallic state.
- Magnetic field restores ferromagnetic metallic state at high pressures.
- Colossal magnetoresistance of ~3×10^11% observed under 5 T at 4 GPa.

## Abstract

The n-type HgCr2Se4 exhibits a sharp semiconductor-to-metal transition (SMT) in resistivity accompanying the ferromagnetic order at TC = 106 K. Here, we investigate the effects of pressure and magnetic field on the concomitant SMT and ferromagnetic order by measuring resistivity, dc and ac magnetic susceptibility, as well as single-crystal neutron diffraction under various pressures up to 8 GPa and magnetic fields up to 8 T. Our results demonstrate that the ferromagnetic metallic ground state of n-type HgCr2Se4 is destabilized and gradually replaced by an antiferromagnetic, most likely a spiral magnetic, and insulating ground state upon the application of high pressure. On the other hand, the application of external magnetic fields can restore the ferromagnetic metallic state again at high pressures, resulting in a colossal magnetoresistance (CMR) as high as ~ 3 * 10^11 % under 5 T and 2 K at 4 GPa. The present study demonstrates that n-type HgCr2Se4 is located at a peculiar critical point where the balance of competion between ferromagnetic and antiferromagnetic interactions can be easily tipped by the external stimuli, providing a new platform for achieving CMR in a single-valent system.