Novel Chiral Magnetic Domain Wall Structure inFe/Ni/Cu(001)Films

Abstract

Using spin-polarized low energy electron microscopy, we discovered a new type of domain wall structure in perpendicularly magnetized Fe/Ni bilayers grown epitaxially on Cu(100). Specifically, we observed unexpected Néel-type walls with fixed chirality in the magnetic stripe phase. Furthermore, we find that the chirality of the domain walls is determined by the film growth order with the chirality being right handed in Fe/Ni bilayers and left handed in Ni/Fe bilayers, suggesting that the underlying mechanism is the Dzyaloshinskii-Moriya interaction at the film interfaces. Our observations may open a new route to control chiral spin structures using interfacial engineering in transition metal heterostructures.

Chirality-Induced Asymmetric Magnetic Nucleation inPt/Co/AlOxUltrathin Microstructures

“…Indeed, the peculiarities of field and current-induced dynamics of domain walls in such samples [13][14][15] have been found to be consistent with a chiral texture localized on the DW, deriving from the presence of interface-induced DMI [16]. These local chiral magnetization textures, that appear as Néel walls of a fixed chirality, have also been observed recently by lowenergy electron microscopy [17,18], on samples with wide domain walls.In this Letter we show that chiral interactions can also be detected at the edges of a microstructure: in the presence of an additional in-plane field, nucleation of reversed domains takes place preferentially at one edge of the sample, oriented perpendicular to this field. The side at which nucleation takes place depends on the direction of both the additional field and the initial magnetization.…”

Unlocking Bloch-type chirality in ultrathin magnets through uniaxial strain

“…2g, where a peak showing a narrow distribution of the angle a appears at B þ 45°. Although this is clearly a chiral spin structure, it neither corresponds to chiral Néel wall [15][16][17] nor to non-chiral Bloch wall [1][2][3]16,17 . This DW spin texture can be understood as a superposition of the lefthanded chiral Néel structure and left-handed chiral Bloch structure, that is, as in Néel walls the spin vector tilts towards the in-plane normal direction of the DW while, at the same time, it rotates around the DW normal as it does in Bloch walls.…”

“…Here Bloch chirality gradually vanishes when f approaches ± 90°(ref. 16). The gradual deviation from sinusoidal behaviour is interesting because, given that the DMI stabilizes the Bloch-type chirality, measuring how the system evolves from mixed chiral textures at small f to non-chiral Bloch DWs at f ¼ ± 90°offers a way to estimate the strength of the DMI (see Supplementary Note 1).…”

“…In the case of interfacial DMI, D ij is restricted to be perpendicular to the position vector r ij ¼ r i À r j (refs 6-9). For this reason, interfacial DMI alone can only stabilize Néel-type chiral spin textures, such as cycloidal spin spirals [10][11][12] , skyrmions 13,14 or chiral Néel walls [15][16][17] . In Bloch-type spin textures, the cross-product (S i  S j ) is parallel to the position vector r ij and E DM vanishes, consequently Bloch walls are usually non-chiral.…”

Reduced-dimensionality-induced helimagnetism in iron nanoislands

“…Our ab initio calculations exclude the role of SOI on the formation energy of our SH. The negligible contribution of SOI in the Fe-b system is ascribed to the small spin-orbit coupling strength of the 3d elements Fe and Cu, which is expected to be an order of magnitude weaker than that of 5d components 30 (for example, W or Ir). The compilation of the J i,j elucidates the physical origin of SH formation in this system.…”