Antisymmetric magnetoresistance and helical magnetic structure in a compensated Gd/Co multilayer

Abstract

Using spin-dependent specular and off-specular polarized neutron reflectivity (PNR), we report the observation of a twisted helical magnetic structure with planar 2\ensuremath{\pi} domain walls (DWs) and highly correlated magnetic domains in a Gd/Co multilayer. Specular PNR with a polarization analysis reveals the formation of planar 2\ensuremath{\pi} DWs below a compensation temperature (${T}_{\mathrm{comp}}$), resulting in a negative exchange bias in this system. Off-specular PNR with spin polarization showed the development of magnetic inhomogeneities (increase in magnetic roughness) for the central part (thickness $\ensuremath{\sim}25--30\phantom{\rule{0.16em}{0ex}}\AA{}$) of each Gd layer, where magnetization is aligned perpendicular (in plane) to an applied field. This is contributing towards an antisymmetric magnetoresistance at ${T}_{\mathrm{comp}}$ in the system. The magnetic roughness is vertically correlated and results in a Bragg sheet observed in the spin-flip channel of off-specular PNR data. The growth and tunability of highly correlated magnetic inhomogeneities (roughness) and the domain structure around ${T}_{\mathrm{comp}}$ in a combination of a twisted helical magnetic structure with planar 2\ensuremath{\pi} DWs will be key for applications in all-spin-based technology.