Magnetic phase diagram of La$_{2-x}$Sr$_{x}$CoO$_{4}$ revised using muon-spin relaxation

TL;DR

This study uses muon-spin relaxation to revise the magnetic phase diagram of La$_{2-x}$Sr$_{x}$CoO$_{4}$, revealing that small hole concentrations significantly affect magnetic ordering and stripe phases.

Contribution

The paper provides a revised magnetic phase diagram of La$_{2-x}$Sr$_{x}$CoO$_{4}$ based on $bc$SR data, highlighting the sensitivity of magnetic order to hole doping and extending the known stripe phase range.

Findings

Magnetic ordering temperature is highly sensitive to small hole concentrations.

Stripe ordered phase extends to lower x than previously thought.

Charge doping above x=0.67 suppresses magnetic order above 1.5 K.

Abstract

We report the results of a muon-spin relaxation ($\mu$SR) investigation of La$_{2-x}$Sr$_{x}$CoO$_{4}$, an antiferromagnetic insulating series which has been shown to support charge ordered and magnetic stripe phases and an hourglass magnetic excitation spectrum. We present a revised magnetic phase diagram, which shows that the suppression of the magnetic ordering temperature is highly sensitive to small concentrations of holes. Distinct behavior within an intermediate $x$ range ($0.2 \leq x \lesssim 0.6$) suggests that the putative stripe ordered phase extends to lower $x$ than previously thought. Further charge doping ($0.67 \leq x \leq 0.9$) prevents magnetic ordering for $T \gtrsim 1.5~{\rm K}$