Using spin dependent specular and off-specular polarized neutron reflectivity (PNR), we report the observation of a twisted helical magnetic structure with planar 2π domain wall (DW) and highly correlated magnetic domains in a Gd/Co multilayer. Specular PNR with polarization analysis reveals the formation of planar 2πDWs below a compensation temperature (T Comp ), resulting to positive exchange bias in this system. Off-specular PNR with spin polarization showed development of magnetic inhomogenities (increase in magnetic roughness) for central part (thickness ~ 25-30 Å) of each Gd layer, where magnetization is aligned perpendicular (in-plane) to an applied field. These magnetic roughness are vertically correlated and results into Bragg sheet in spin flip channel of Offspecular PNR data, which is contributing towards an antisymmetric magnetoresistance at T Comp in the system. The growth and tunability of highly correlated magnetic inhomogeneities (roughness) and domain structure around T Comp in combination of twisted helical magnetic structure with planar 2πDWs will be key for application in all-spin-based technology.The current-induced manipulation of magnetic order through spin-orbit torque (SOT) has recently attracted great interest for the realization of magnetic memory and logic application devices with fast switching [1][2][3][4][5]. The Dzyaloshinskii-Moriya interaction [6], and the spin Hall effect via heavy-metal layers [7-9] were the major phenomena that attributed for large chiral spin torques. Exchange coupling torque (ECT) recently showed a significant enhancement of the spin-torque efficiency in artificial antiferromagnetic (AF) structures [10,11], which allows moving nanoscale magnetic domain walls (DW) with current at large velocities [10].The compensated rare earth (RE)-transition metal (TM) alloys and heterostructures,where the RE and TM moments are aligned antiparallel due to the strong AF interaction and the total net moment tends to zero, are potential candidate materials for realizing devices with higher speed and density [12][13][14][15][16]. A class of ferrimagnets consisting of RE-TM alloys and heterostructures also have the potential to exhibit DW motion via an ECT [17,18]. Fast switching in compensated systems can further be influenced by magnetic [16,19] and optical [20] fields. Recently Vedmedenko et al. [21], have pointed out theoretically that nano-sized stable magnetic helices can be used for magnetic energy storage. Realization of magnetic helices with stable magnetic properties have also been studied theoretically [22] and experimentally [23] in exchange-coupled thin films and RE/TM multilayers, respectively. It is recognized that magnetization reversal and a magnetic helical configuration (planar 2πDWs) in RE-TM multilayer with no external magnetic field around the compensation temperature (T Comp , the temperature at which total moments of RE-TM multilayer tend to zero) is the key to manipulating magnetic devices [20,23]. However the response of interface DWs in RE-TM heterostr...

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Antiferromagnetic coupling between rare-earth and transition metal ferromagnetic layers gives rise to various magnetic ground states in heterostructures of these materials. Interface structure and morphology tend to play important roles in magnetic properties of such systems. Interface induced magnetization in Gd/Co heterostructures has been studied using a combination of structural and magnetic characterization techniques. The interface morphology of the Gd/Co system was varied by growing Gd/Co multilayers using magnetron sputtering under different argon partial pressures. Interfacial properties were further modified by annealing the multilayers under high vacuum. The macroscopic magnetization measurements have been correlated with depth dependent structure and magnetic properties of multilayers studied using X-ray and polarized neutron reflectometry techniques. Secondary ion mass spectrometry measurements from both as-deposited and annealed samples also confirmed modification at the interfaces. It has been shown that the interface structure, together with roughness, leads to a unique low-temperature magnetic phase characterized by twisting of Gd and Co moments.