Magnetic structures determined by neutron diffraction in the EuB ϵ−xC x system

Abstract

Magnetic structures of pure and carbon-doped europium hexaboride EuB 6−xC x, were determined by neutron diffraction on powders prepared from 11B and 153Eu. EuB 6 is a simple ferromagnet, whereas the x = 0.20 compound has an incommensurate spiral structure with propagation vector τ = (0.28, 0, 0). Data for a magnetically inhomogeneous intermediate composition, x = 0.05, indicate a mixture of ferromagnetic and helimagnetic domains with τ = (0, 0, 0.104). Helimagnetism in EuB 6−xC x arises from a competition between ferromagnetic near-neighbour exchange and antiferromagnetic interactions due to conduction electrons.