Oral
28 Oct 2023
The Dzyaloshinskii-Moriya interaction (DMI) is an antisymmetric exchange that stabilizes magnetization textures, such as skyrmions and merons, assists spin-orbit torques, and modifies several magnetic properties [1,2]. The DMI was predicted in 1958 [3], but the emergence of this coupling in complex materials and interfaces, as well as the tunning of its strength and symmetries, are still under active investigation. This presentation investigates the DMI of metals and interfaces containing rare-earth atoms (lanthanides), such as Dy and Tb. These atoms are heavy and possess a strong spin-orbit interaction which induces antisymmetric exchange, i.e., a DMI [4,5]. The starting point of our study is a model consisting of two magnetic atoms in an electron gas, one of them being a rare earth [5]. Each atom creates a conduction-electron spin polarization along its spin direction, but the rare earth tilts this spin polarization due to the spin-orbit coupling [5]. The result is an anisotropic spin density, orthogonal to both atomic spins, that we name Dzyaloshinskii-Moriya Spin Density (DM-SD). Figure 1 shows this spin density. Then, when adding a third impurity to the electron gas, its spin locally interacts with the DM-SD giving rise to the DMI. Therefore, the DM-SD is the antisymmetric equivalent of the RKKY spin density that mediates the isotropic exchange between two distant spins in metals. The simplicity of this model allows its use in more general situations, such as rare-earth-containing interfaces between magnetic insulators and transition-metal magnets. Furthermore, if the rare-earth atom is replaced by a transition metal with a partially unquenched orbital momentum, the magnitude of the DM-SD is reduced from the one of rare earths. AOL acknowledges financial support in Chile from ANID FONDECYT 11230120.References: [1] S. Blundell, Magnetism in Condensed Matter (Oxford University Press, Oxford, 2012). [2] Spintronics Handbook: Spin Transport and Magnetism: Volume One: Metallic Spintronics, edited by E. Y. Tsymbal and I. Zutic (CRC, Boca Raton, FL, 2019). [3] I. Dzyaloshinsky, A thermodynamic theory of “weak” ferromagnetism of antiferromagnetics, J. Phys. Chem. Solids 4, 241 (1958). [4] S. M. Goldberg and P. M. Levy, Anisotropy in binary metallic spin-glass alloys. II. Rare earths, Phys. Rev. B 33, 291 (1986). [5] A. B. Cahaya and A. O. Leon, Dzyaloshinskii-Moriya spin density by skew scattering, Phys. Rev. B 106, L100408 (2022).
