Magnetic properties of Fe-substituted NiBr2 single crystals

NiBr 2 is a multiferroic material with an incommensurate magnetic ground state that has easy-plane anisotropy. This manuscript reports how the magnetic properties evolve with Fe substitution in Ni 1 − x Fe x Br 2 single crystals for 0 ≤ x ≤ 0.17. A particular emphasis is placed on the x = 0.055 crystal, for which H v s . T magnetic phase diagrams were developed on the basis of anisotropic magnetization measurements. The observed phase evolution reveals a phase transition in the x = 0.055 crystal that is not present in NiBr 2 . The data also demonstrate that the easy-plane anisotropy of NiBr 2 is altered by Fe substitution, with a finite easy-axis anisotropy developing at even the low concentration of x = 0.055. These results demonstrate that Fe substitution enables a fine-tuning of the magnetism in NiBr 2 , especially the magnetic anisotropy, and may therefore promote complex magnetic phases. • The anisotropy of NiBr 2 is found to be modified by Fe substitution, with an out-of-plane component of the ordered moment seeming to form in the incommensurate ground state for certain Fe contents. • An additional temperature-dependent phase transition has been identified in the Fe-substituted compounds. • Magnetic phase diagrams have been produced for a crystal with 5.5% Fe relative to Ni, and these reveal the complex evolution of the magnetic phases with temperature and applied field.