Temperature dependence of the propagation vector in Ni3−xCoxV2O8 with x=0.1 and 0.5

• There is a feature in concentration dependence of the propagation vector at x≈0.75x≈0.75.
• Doping with 3.3% of Co crushes a temperature dependence of the propagation vector.
• Doping with 16.5% of Co induces the new temperature dependence of the wave vector.

We present the susceptibility and neutron diffraction data on multiferroic Ni3−xCoxV2O8 with x=0.1 and 0.5. The temperature dependence of the susceptibility indicates that the magnetic order–disorder transition occurs at THTI=8.5 K in both samples. Below THTI, the high-temperature incommensurate magnetic structure is realized, which undergoes a transition to the low-temperature incommensurate phase when the sample is cooled. The temperature evolution of the propagation vector k for x=0.1 is very weak, which confirms previous studies showing that substitution of 3.5% Ni ions by Co ions suppresses the explicit temperature dependence of k that is observed in the parent compound. On the other hand, we found that the vector k for x=0.5 exhibits a definite temperature dependence, which differs from the case of the undoped sample (x=0).