Ruderman–Kittel–Kasuya–Yosida-type interfacial Dzyaloshinskii–Moriya interaction in heavy metal/ferromagnet heterostructures

Abstract

The manipulation of magnetization with interfacial modification using various spin-orbit coupling phenomena has been recently revisited due to its scientific and technological potential for next-generation memory devices. Herein, we experimentally and theoretically demonstrate the interfacial Dzyaloshinskii–Moriya interaction characteristics penetrating through a MgO dielectric layer inserted between the Pt and CoFeSiB. The inserted MgO layer seems to function as a chiral exchange interaction mediator of the interfacial Dzyaloshinskii–Moriya interaction from the heavy metal atoms to ferromagnet ones. The potential physical mechanism of the anti-symmetric exchange is based on the tunneling-like behavior of conduction electrons through the semi-conductor-like ultrathin MgO. Such behavior can be correlated with the oscillations of the indirect exchange coupling of the Ruderman–Kittel–Kasuya–Yosida type. From the theoretical demonstration, we could provide approximate estimation and show qualitative trends peculiar to the system under investigation.

Tuning the interfacial Dzyaloshinskii–Moriya interaction in perpendicularly magnetized CoFeB system

“…Since DMI also decreases with annealing temperature, we attribute the source of this behaviour to a positive correlation between DMI and PIM [44][45][46]. Alternatively, within the RKKY-like iDMI model [47] where chirality is induced by the interfacial Rashba coupling [48], the non-magnetic B-rich segregated layer can mediate the iDMI between the CoFe-rich FM and Pt-rich HM layers. Using a toy model bearing semblance to that used by Bruno to explain RKKY-like interlayer exchange coupling in GMR stacks, [47] has shown that if this layer is also conducting, then it can suppress iDMI due to its screening effect.…”

“…Alternatively, within the RKKY-like iDMI model [47] where chirality is induced by the interfacial Rashba coupling [48], the non-magnetic B-rich segregated layer can mediate the iDMI between the CoFe-rich FM and Pt-rich HM layers. Using a toy model bearing semblance to that used by Bruno to explain RKKY-like interlayer exchange coupling in GMR stacks, [47] has shown that if this layer is also conducting, then it can suppress iDMI due to its screening effect. Similar reports of suppressed iDMI and K eff upon addition of metallic spacer layers have been reported [44,47,49,50].…”

“…Using a toy model bearing semblance to that used by Bruno to explain RKKY-like interlayer exchange coupling in GMR stacks, [47] has shown that if this layer is also conducting, then it can suppress iDMI due to its screening effect. Similar reports of suppressed iDMI and K eff upon addition of metallic spacer layers have been reported [44,47,49,50]. Furthermore, the intermixing effect, understood within the real space spin-spiral based DMI model [37], can microscopically alter the hybridization of 3d-5d bands around the Fermi level in a complicated way.…”

XMCD and ab initio study of interface-engineered ultrathin Ru/Co/W/Ru films with perpendicular magnetic anisotropy and strong Dzyaloshinskii–Moriya interaction

“…12 If a thin MgO spacer separates the HM and FM layers, then the Ruderman-Kittel-Kasuya-Yosida-type interfacial DMI can be induced. 13 The primary consideration in this field is related to ideal structural interfaces. Little attention has been paid to the disordered structure of thin films, 14,15 where the layers have surface roughness and undergo intermixing at the interfaces.…”

“…12 If a thin MgO spacer separates the HM and FM layers, then the Ruderman–Kittel–Kasuya–Yosida-type interfacial DMI can be induced. 13…”