Chiral-fluctuations mediated helical to paramagnetic phase transition and scaling study in β-Mn type Co₈Zn₈Mn₄ chiral magnet

Abstract

We report detailed magnetization and ac susceptibility studies on a chiral cubic β-Mn type Co8Zn8Mn4 alloy near the onset of magnetic ordering temperature. The Co8Zn8Mn4 alloy undergoes a complex series of temperature-driven transition from paramagnetic to helimagnetic phase through an intermediate inhomogeneous chiral fluctuations phase. The Gaussian shaped peak in χ′(T, H = 0 Oe) at THM ∼= 343.19 K is analogous to that of the zero-field transition to long-period modulated helical state. Moreover, a pronounced field-induced anomaly in χ′(T, H ≥ 500 Oe) rises quickly with field above THMlike a fingerprint, evident of a field-induced crossover into a precursor region. The in-field critical behaviour characterizing a ferromagneticparamagnetic phase transition in the vicinity of ordering temperature confirms that Co8Zn8Mn4chiral magnet belongs to the 3D-Heisenberg universality class. The existence of precursor region and the sizable expansion in the transition temperature, TC can be explained by the Landau equation.