Abstract
Chiral spin textures of a ferromagnetic layer in contact to a heavy non-magnetic metal, such as Néel-type domain walls and skyrmions, have been studied intensively because of their potential for future nanomagnetic devices. The Dyzaloshinskii–Moriya interaction (DMI) is an essential phenomenon for the formation of such chiral spin textures. In spite of recent theoretical progress aiming at understanding the microscopic origin of the DMI, an experimental investigation unravelling the physics at stake is still required. Here we experimentally demonstrate the close correlation of the DMI with the anisotropy of the orbital magnetic moment and with the magnetic dipole moment of the ferromagnetic metal in addition to Heisenberg exchange. The density functional theory and the tight-binding model calculations reveal that inversion symmetry breaking with spin–orbit coupling gives rise to the orbital-related correlation. Our study provides the experimental connection between the orbital physics and the spin–orbit-related phenomena, such as DMI.
Highlights
Chiral spin textures of a ferromagnetic layer in contact to a heavy non-magnetic metal, such as Néel-type domain walls and skyrmions, have been studied intensively because of their potential for future nanomagnetic devices
It has been demonstrated that the Dyzaloshinskii–Moriya interaction (DMI) at the interface between ferromagnetic (FM) and nonmagnetic heavy metals (HMs) plays a major role for the formation of chiral spin textures, such as skyrmions[3,4] and homochiral Néel-type domain walls (DWs)[5,6,7], which are attractive for the development of future information storage technology[8]
The ratio m?o =mko increases by 53% as D increases, and mD shows a clear correlation with the DMI; mDð100KÞ=mDð300KÞ≈ 6.4. Because both orbital anisotropy and mD are closely related to the orbital occupation with ISB28,37,38, these results suggest that the temperature dependence of DMI is governed by the change in asymmetric electron occupation in orbitals in addition to spin magnetic moments as we discuss with the following theoretical studies
Summary
Chiral spin textures of a ferromagnetic layer in contact to a heavy non-magnetic metal, such as Néel-type domain walls and skyrmions, have been studied intensively because of their potential for future nanomagnetic devices. It has been reported that the spin chirality is a manifestation of the chirality of the orbital magnetism in strongly spin–orbit coupled systems with ISB21,22 These previous studies suggest a possible microscopic origin of the interfacial DMI, which has remained experimentally unaddressed so far. Changing the temperature of the system allows for charge redistribution between in-plane and out-of-plane orbitals while preserving the integrity of electronic states of the trilayer unlike other interface control methods such as ion irradiation[26] or thermal annealing technique[27], which may cause a permanent atomic rearrangement and induce undesired extrinsic effects To discuss this temperature dependence of the DMI, that of the spin (ms) and orbital (mo) magnetic moments of Co and Pt is studied by X-ray magnetic circular dichroism (XMCD) spectroscopy. We find that the perature out-of-plane dependence orbital moment
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