Scaling behaviour of magnetic transitions in Ni₃V₂O₈

Abstract

We have studied phase transitions in multiferroic Ni₃V₂O₈, through dielectric measurements and by investigating the effects of Zn doping. The divergence of the dielectric constant near T _L = 6.4 K can be approximately fit by power law behaviour, but exhibits different critical exponents above and below T _L . The two higher temperature magnetic transitions in (Ni_1−x Zn _x )₃V₂O₈, are strongly suppressed as the Zn doping fraction x is increased. The rates of the suppression of both T _H and T _L with x are consistent with two-dimensional spin systems, with the suppression of T _H consistent with Ising spins and the suppression of T _L consistent with Heisenberg spins.

Keywords:

• multiferroic
• magnetoelectric
• phase transitions
• doping
• critical exponent
• antiferromagnet
• two-dimensional

Acknowledgements

We would like to thank A.B. Harris for helpful conversations during the course of this work. This research was supported by the National Science Foundation under NSF CAREER DMR-06044823 and by the Institute for Materials Research at Wayne State University.