Electrical detection of spiral spin structures in Pt|Cu_2OSeO_3 heterostructures

TL;DR

This paper investigates the electrical detection of complex spin structures in Cu_2OSeO_3 using spin-Hall magnetoresistance and spin Seebeck effect, revealing phase-dependent behaviors and control mechanisms in heterostructures with platinum.

Contribution

It demonstrates the sensitivity of SMR to surface magnetization changes in spin-spiral phases and explores the control of SMR and SSE behaviors in Cu_2OSeO_3 heterostructures.

Findings

SMR changes drastically at phase transitions between helical and conical spirals

SMR sign and magnitude are controllable via cone angle in the conical phase

SSE exhibits unconventional behavior with phase and magnitude variations

Abstract

The interaction between the itinerant spins in metals and localized spins in magnetic insulators thus far has only been explored in collinear spin systems, such as garnets. Here, we report the spin-Hall magnetoresistance (SMR) sensitive to the surface magnetization of the spin-spiral material, Cu_2OSeO_3. We experimentally demonstrate that the angular dependence of the SMR changes drastically at the transition between the helical spiral and the conical spiral phases. Furthermore, the sign and magnitude of the SMR in the conical spiral state are controlled by the cone angle. We show that this complex behaviour can be qualitatively explained within the SMR theory initially developed for collinear magnets. In addition, we studied the spin Seebeck effect (SSE), which is sensitive to the bulk magnetization. It originates from the conversion of thermally excited low-energy spin waves in the magnet, known as magnons, into the spin current in the adjacent metal contact (Pt). The SSE displays unconventional behavior where not only the magnitude but also the phase of the SSE vary with the applied magnetic field.