Critical phenomena in helical magnet β-MnO₂: X-ray magnetic scattering study

It has been theoretically expected that critical phenomena of helimagnetism is drastically different from those of collinear antiferromagnetism due to the existence of chiral degree of freedom. In order to verify this prediction, we carried out X-ray magnetic scattering measurements on a simplest helimagnet β-MnO₂ using a synchrotron radiation. The critical exponent β was estimated at 0.25 ± 0.05 from the temperature dependence of the scattering intensity. This value is consistent with the predicted value 0.253 for chiral system rather than with 0.346 for collinear system.