The compound NiBr2 crystallizes in the trigonal space group R-3m. Below TN= 44 K, NiBr2 exhibits antiferromagnetic order characterized by antiferromagnetically stacked sheets of ferromagnetically aligned Ni spins. A transition to a helical magnetic structure occurs below TIC=22.8 K with a propagation vector of at 4.2 K. Here we use neutron diffraction to study the tuning of the magnetic properties with cobalt substitution in single crystals for several compositions of Ni1-xCoxBr2, where x = 0, 0.2, 0.25, 0.3, and 0.45. Our measurements show that the TN decreases with doping while changes in TIC are more subtle. The neutron scattering studies further reveal that the 6 incommensurate spots in the parent compound give way to a ring of magnetic scattering reminiscent of that observed previously for Ni0.92Zn0.08Br2.This work was supported by U.S. DOE, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division and the Gordon and Betty Moore Foundation's EPiQS Initiative.
APS March Meeting Abstracts
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