Theoretical proposal predicting anomalous magnetoresistance and quadratic Hall effect in the partially ordered state of MnSi

TL;DR

This paper presents a theoretical model predicting unique magnetoresistance and Hall effect behaviors in the partially ordered magnetic state of MnSi, explaining experimental anomalies without net magnetization.

Contribution

It explicitly predicts anomalous magneto-transport properties of the proposed magnetic structure in MnSi's partially ordered state, including linear magnetoresistivity and quadratic Hall conductance.

Findings

Magnetoresistivity is linear in magnetic field.

Hall conductance is quadratic in magnetic field.

Predicted anisotropy and Hall voltage orientations in specific geometries.

Abstract

In [B. Binz, A. Vishwanath and V. Aji, Phys. Rev. Lett. 96, 207202 (2006)], a magnetic structure that breaks time reversal symmetry in the absence of net magnetization was proposed as an explanation for the high pressure "partially ordered" state of MnSi. Here we make explicit the anomalous magneto-transport properties of such a state: a magnetoresistivity which is linear and a Hall conductance which is quadratic in the applied magnetic field. Field cooling procedures for obtaining single domain samples are discussed. The anomalous effects are elaborated in the case of three geometries chosen to produce experimentally unambiguous signals of this unusual magnetic state; e.g., it is predicted that a field in z-direction induces an anisotropy in the x-y plane. Another geometry leads to a Hall voltage parallel to the magnetic field.