Evidence for Noncollinearity between Surface and Bulk Magnetization in Ultrathin Co Films

Abstract

The magnetization reversal of ultrathin Co films on Cu(001) has been investigated by grazing ion scattering and magneto-optical Kerr effect. Differences in the behavior of surface and bulk magnetization are found and attributed to the reduced coordination and site symmetry at the surface. The reversal behavior of the surface magnetization depends on the chemical surface composition. For pure Co films, the reversal of the bulk magnetization is preceded by a complete reversal of the surface magnetization. A particular magnetic state of the surface is suggested as a precursor for magnetization reversal.

Surface Spin-Valve Effect

“…14,15 The fundamental physics involved is that the interface spins have a lower coordination number and therefore fewer exchange bonds compared to the bulk spins. This can lead to a reconstruction of the interface spin order, resulting in quite different magnetic moment and anisotropy.…”

Magnetic interface coupling between ultrathin Co andNixMn100−xfilms on Cu(001)

“…However, experimental studies on thin ferromagnetic films with a thickness of several monolayers to about 100 Å, confirm significant differences in the orientation of the interface and bulk magnetization during reversal in an external magnetic field. These findings have either been attributed to weakened exchange interactions at the interface 43,62 or to interface-induced anisotropies. 63 If a ferromagnetic layer is exchange coupled to an antiferromagnetic layer, differences in the direction of the surface, interface, and bulk magnetization can occur due to the AFMinduced anisotropy at the AFM/FM interface and the formation of partial domain walls within the ferromagnetic film parallel to the surface.…”

“…Such a method is the detection of polarized fluorescence light emitted from He atoms which are excited by EC during grazing scattering from a surface. 13,[38][39][40][42][43][44][45] Under defined conditions, EC hysteresis loops are obtained by monitoring the Stokes parameter S / I as a function of the external magnetic field. The reversible part of the surface magnetization is related to the normalized parameter ⌬S / I = S / I͑ ↑ ͒ − S / I͑ ↓ ͒ with the Stokes parameter S / I͑ ↑ ͒ and S / I͑ ↓ ͒ for reversed settings of the magnetization.…”

Predicting epitaxial orientations and lattice structure in ultrathin magnetic thin films

“…C Magnetic properties and performances of metallic thin film magnets such as magnetic anisotropy, magnetization reversal processes, and domain wall magneto-resistance are crucial for designing spintronic devices. [1][2][3][4] In particular, magnetic ultra-thin films made of 3d transition metals, e.g., cobalt (Co), 5,6 iron (Fe), 7,8 and nickel (Ni), 9,10 have been investigated extensively in order to obtain the desirable characteristics for specific applications. Compared with the bulk, the magnetic moment and anisotropies of ultrathin films are remarkably different and sensitively dependent on the crystal structure and thermal stability of the film.…”