Magnetic fluctuations and two-dimensional ordering in ErBa2Cu3O7

Abstract

Neutron-diffraction and small-angle scattering techniques have been used to study the magnetic properties of Er${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$. Below the superconducting transition of 95 K there is a decrease in the small-angle scattering, which has the correct amplitude, temperature dependence, and $q$ dependence to be interpreted as the screening of the paramagnetic fluctuations by the superconducting electrons. At low temperatures (∼½ K) the Er moments become ordered two dimensionally, with chains of spins coupled ferromagnetically, while adjacent chains align antiparallel.