Evidence of spin density waves in La$_3$Ni$_2$O$_{7-\delta}$

TL;DR

This study provides evidence of magnetic order in La$_3$Ni$_2$O$_{6.92}$, a nickelate related to superconducting La$_3$Ni$_2$O$_{7- ext{delta}}$, using muon spin relaxation, revealing spin density wave behavior.

Contribution

First muon spin relaxation study showing magnetic order and spin density waves in La$_3$Ni$_2$O$_{6.92}$ at ambient pressure.

Findings

Magnetic order exists at T_N=154 K in La$_3$Ni$_2$O$_{6.92}$.

Bulk magnetism confirmed by transverse field measurements.

Oxygen deficiencies affect magnetic field distribution.

Abstract

The recently discovered superconductivity with critical temperature $T_c$ up to 80 K in the double-layer Nickelate La$_3$Ni$_2$O$_{7-\delta}$ under pressure has drawn great attention. Here we report the positive muon spin relaxation ($\mu^+$SR) study of polycrystalline La$_3$Ni$_2$O$_{6.92}$ under ambient pressure. Zero-field $\mu^+$SR experiments reveal the existence of magnetic order in La$_3$Ni$_2$O$_{6.92}$ with $T_{N}=154\ \rm{K}$. The weak transverse field $\mu^+$SR measurements confirms the bulk nature of magnetism. In addition, a small quantity of oxygen deficiencies can greatly broaden the internal magnetic field distribution sensed by muons.