Magnetic structure of the S=1 Ni5 (Te O3) 4 Br2 layered system governed by magnetic anisotropy

Abstract

Magnetization, neutron diffraction, and antiferromagnetic resonance measurements were employed to investigate the magnetic ground state of Ni5 (Te O3) 4 Br2 single crystal. Despite the layered topology of the Ni2+ sites, typical for frustrated antiferromagnets, the system orders antiferromagnetically below TN =29 K. Noncollinear arrangements of the Ni sublattices having a very complex temperature dependence were found from the neutron diffraction and magnetization measurements. Single-ion anisotropy, associated with the strongly distorted Ni-centered octahedra, has the same magnitude as the antiferromagnetic exchange interaction. The effect of these anisotropies prevails over the geometrical frustration leading to a long-range magnetic ordering below TN. © 2007 The American Physical Society.