Observation of Magnetic Order in a ${\rm YBa_2Cu_3O_{6.6}}$ Superconductor

TL;DR

This study uses polarized neutron scattering to detect a magnetic transition in YBa2Cu3O6.6 at 235K, aligning with the pseudogap phase, revealing magnetic order with specific properties.

Contribution

It provides direct evidence of magnetic order associated with the pseudogap transition in a high-temperature superconductor using neutron scattering.

Findings

Magnetic transition occurs at about 235K

Magnetic moment is approximately 0.1 μB per sublattice

Correlation length exceeds 75 Å

Abstract

Polarized beam neutron scattering measurements on a highly perfect crystal of ${\rm YBa_2Cu_3O_{6.6}}$ show a distinct magnetic transition with an onset at about 235K, the temperature expected for the pseudogap transition. The moment is found to be about 0.1 $\mu_B$ for each sublattice and have a correlation length of at least 75 \AA. We found the critical exponent for the magnetic neutron intensity to be 2$\beta$ =0.37$\pm$ 0.12. This is the proper range for the class of transition that has no specific heat divergence possibly explaining why none is found at the pseudogap transition.