Magnetic ordering in Eu2CuO4.

Abstract

Neutron-diffraction experiments have been performed to study the magnetic ordering of Cu ions in a single crystal of ${\mathrm{Eu}}_{2}$${\mathrm{CuO}}_{4}$. Magnetic reflections corresponding to the wave vector k=(1/2,1/2,0) develop below the N\'eel temperature ${\mathit{T}}_{\mathit{N}}$=265(5) K, showing a long-range antiferromagnetic ordering of Cu moments in ${\mathrm{Eu}}_{2}$${\mathrm{CuO}}_{4}$. The low-temperature saturated moment was determined to be (0.4\ifmmode\pm\else\textpm\fi{}0.1)${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$, with the spin direction restricted to the a-b plane. Magnetic-field-dependent studies show no hysteretic behavior at intermediate temperatures, which strongly suggests that the antiferromagnetic spin structure is of the noncollinear double-k type previously observed in ${\mathrm{Sm}}_{2}$${\mathrm{CuO}}_{4}$ and also in ${\mathrm{Nd}}_{2}$${\mathrm{CuO}}_{4}$ at the intermediate temperature. We do not find any evidence of spin reorientation below the N\'eel temperature down to 1.4 K, the lowest temperature investigated.