Topological Contributions to the Anomalous Nernst and Hall Effect in the Chiral Double-Helimagnetic System

TL;DR

This study uses first-principles calculations to show that topological magnetic textures in MnP and FeP significantly enhance anomalous Hall and Nernst effects, with effects strongly dependent on Fermi surface topology and magnetic phase transitions.

Contribution

It demonstrates the temperature-dependent topological contributions to Hall and Nernst effects in chiral double-helimagnetic systems using advanced computational methods.

Findings

Hall and Nernst effects are enhanced due to magnetic textures.

Magnetic phase transitions influence topological effects.

Topological effects depend on Fermi surface topology.

Abstract

MnP and FeP are show complex magnetic spiral states with geometric phase contributions to the anomalous Hall effect and the topological Hall effect, where both have thermoelectric Nernst counterparts. We use state of the art first principle calculations to show that both Hall and Nernst effects are enhanced in MnP and FeP due to the temperature dependent magnetic texture. At ambient pressure the inversion breaking crystals shows a transition from a double-spiral helimagnetic phase to a topologically trivial magnetic phase. This helimagnetic structure is determined by exchange frustration and the Dzyaloshinskii-Moriya interaction. In the presence of an external magnetic field the magnetic structure transforms into a fan-like phase with a finite spin chirality that gives rise to an effective magnetic field on the order $\sim$1 T. The topological Hall and Nernst effect from this field are comparable or larger to tightly-wound skyrmion systems. Lastly, we show that the topological effects are strongly dependent on the Fermi surface topology, which has strong variations and even sign changes for similar magnetic textures.