Critical analysis of skyrmionic material Co6.5Ru1.5Zn8Mn4: A complex interplay of short and long-range interactions around the transition temperature

Abstract

In contrast to the critical behaviour study in magnetism which is well known and important owing to its application for understanding the nature of underlying spin-spin interactions, magnetotransport based critical studies are rare in literature, although it has advantages from bulk to mesoscopic magnetic devices. In this article, we report the novel manifestation of crossover behaviour between two universality classes governing spin interaction across the ferromagnetic Curie temperature TC in critical scaling of anomalous hall conductivity (AHC) isotherms for a skyrmion-hosting itinerant ferromagnet Co6.5Ru1.5Zn8Mn4. Along with the magnetotransport, the traditional critical scaling of magnetic isotherms yields β = 0.423 ± 0.004, γ = 1.08 ± 0.016, and δ = 3.553 ± 0.009 suggesting the 3D Heisenberg and Mean Field type of spin interactions below and above TC, respectively. The isotropic magnetic exchange strength decays as J(r) ≈ r−4.617, implying the prevalence of crossover from long-range ordering to short-range type interaction. In addition, the existence of a fluctuation-disordered magnetic phase immediately below TC and a skyrmion pocket bounded by conical-helical phases have been observed in the magnetocaloric effect. The novel approach of generating a low-field phase diagram employing the quantitative criterion of phase transition from the scaling of isothermal magneto-entropic change (ΔSm) shows an excellent convergence with the phase boundaries obtained from conventional magnetic and AHC scaling. This simultaneous scaling of magnetization and AHC isotherms for systems with crossover behaviour establishes the universality of the magnetotransport-based critical scaling approach which still remains in its infancy.