Chiral magnetoresistance in Pt/Co/Pt zigzag wires

Abstract

The Rashba effect leads to a chiral precession of the spins of moving electrons while the Dzyaloshinskii-Moriya interaction (DMI) generates preference towards a chiral profile of local spins. We predict that the exchange interaction between these two spin systems results in a 'chiral' magnetoresistance depending on the chirality of the local spin texture. We observe this magnetoresistance by measuring the domain wall (DW) resistance in a uniquely designed Pt/Co/Pt zigzag wire, and by changing the chirality of the DW with applying an in-plane magnetic field. A chirality-dependent DW resistance is found, and a quantitative analysis shows a good agreement with a theory based on the Rashba model. Moreover, the DW resistance measurement allows us to independently determine the strength of the Rashba effect and the DMI simultaneously, and the result implies a possible correlation between the Rashba effect, the DMI, and the symmetric Heisenberg exchange.In a magnetic system with inversion symmetry breaking combined with spin-orbit coupling (SOC), a variety of chirality-related phenomena occur. For instance, due to the Rashba effect [1], the spins of the conduction electrons flowing at an interface are subject to an effective in-plane magnetic field due to the relativistic SOC, resulting in spin precession around the field during its transport. In this case, the direction of the magnetic field depends on the electron flow direction. In contrast, the precession of the conduction spins, as can be seen from comparing Figs. 1(a) and 1(b), is independent of the flow direction and shares the same rotational sense (denoted by a chirality of electrons, C e ) [2]. Apart from the chiral behavior of the conduction spins, the chiral nature of localized spins has recently been discovered in ferromagnetic materials with inversion asymmetry and SOC. This gives rise to the Dzyaloshinskii-Moriya interaction (DMI) [3,4] leading to a chiral spin texture of the localized spins (C m ), manifested as Néel type magnetic domain walls (DWs) [5] and magnetic skyrmions [6], which are crucial to the future design of spintronic devices.Although these two effects originate in different spin systems, one can speculate about their interplay through exchange interaction between the conduction and localized spins [7][8][9]. This results in a magnetoresistance (MR) which arises when the conduction electron spins propagate with a fixed chirality due to Rashba-type SOC and interact with the chiral DMI-induced magnetic texture. As shown in Figs. 1(c) and 1(d), this should lead to lower (higher) resistance when C e is identical (opposite) to C m . This MR can be termed as 'chiral MR', since the magnitude of the MR varies for spin The chirality of the profile of the spin precession is identical (Ce = +1) for both signs of k. (c)(d) Inside a chiral magnetic texture with chirality Cm (green arrows), the rotation of electron spins generally follow the local spins due to exchange interaction while finite degree of misalignment is inevitable, which gives rise to t...

Magnetic Scattering in Ni Wires Fabricated on Ferroelectric LiNbO3 Substrate for Magnetic Sensor Application

“…Thus, the relatively large MR response observed in transport measurements alludes to the possibility that the spin-dependent scattering mechanism in domains and domain walls occurs. (40,(43)(44)(45)(46)(47)(48) The heterojunction structure composed of ferromagnetic and ferroelectric layers provides a crucial key to investigating the fundamental physical mechanism and producing artificial multiferroic functional materials and devices.…”

“…Recently, the Dzyaloshinskii-Moriya interaction (DMI) (38,39) at the interface has attracted much attention because it facilitates the stabilization of homochiral Néel domain walls. (40) Thus, a domain wall is not only a unique object but also plays a significant role in magnetization reversal and scattering properties. Here, we investigated the fundamental properties of the domains and domain walls formed in the Ni wire fabricated on the singlecrystal lithium niobate (LiNbO 3 ) Y-cut 128° substrate.…”

Rashba Effect in Functional Spintronic Devices

“…[73] Notably, the chiral derivative is a powerful tool to describe the symmetry of DMI and SOT for other types of SOC (i.e., Dresselhaus SOC and Weyl SOC), [74] which is consistent with a microscopic calculation of DMI. [75] It is also useful for describe a chirality of other physical phenomena such as the damping, [76] gyromagnetic ratio, [76] magnetoresistance, [77] and the magnon torque. [78] A qualitative understanding of the interfacial DMI based on the chiral derivative is provided as follows.…”

Domain-wall resistance in CoFeB-based heterostructures with interface Dzyaloshinskii–Moriya interaction

“…We find that such estimation agrees well with the DW resistance for the thick Ta layer films; however, a discrepancy remains for the thinner Ta layer films. Other contribution to the DW resistance, including the recently discovered chiral DW resistance 23 , may account for the discrepancy.…”

“…Recently, it has been reported that a chiral DW resistance appears in system with large spin orbit coupling 23 . Provided a Rashba-like Hamiltonian can describe the electronic states of the heterostructure, an additional DW resistance emerges only when the magnetic configuration is a chiral Néel type.…”