Evidence for strong surface magnetoelastic anisotropy in epitaxial Cu/Ni/Cu(001) sandwiches

Impact of a rubrene buffer layer on the dynamic magnetic behavior of nickel layers on Si(100)

Interfaces of ferromagnetic/organic material hybrid structures refer to the spin interface that governs physical properties for achieving high spin polarization, low impedance mismatch, and long spin relaxation. Spintronics can add new functionalities to electronic devices by taking advantage of the spin degree of freedom of electrons, which makes understanding the dynamic magnetic properties of magnetic films important for spintronic device applications. Our knowledge regarding the magnetic dynamics and magnetic anisotropy of combining ferromagnetic layer and organic semiconductor by microwave-dependent magnetic measurements remains limited. Herein, we report the impact of an organic layer on the dynamic magnetic behavior of nickel/rubrene bilayers deposited on a Si(100) substrate. From magnetic dynamic measurements, opposite signs of effective magnetic fields between the in-plane (IP) and out-of-plane (OP) configurations suggest that the magnetization of Ni(x)/rubrene/Si prefers to coexist. A shift in OP resonance fields to higher values can mainly be attributed to the enhanced second-order anisotropy parameter K2 value. Based on IP measurements, a two-magnon scattering mechanism is dominant for thin Ni(x)/rubrene/Si bilayers. By adding a rubrene layer, the highly stable IP combined with the tunable OP ferromagnetic resonance spectra for Ni(x)/rubrene/Si bilayers make them promising materials for use in microwave magnetic devices and spintronics with controllable perpendicular magnetic anisotropy.

Structure and magnetic properties of Ni/Cu/Fe/MgO(001) films

The structural and magnetic properties of thin Ni films grown on Cu/Fe/MgO(001) and Cu/MgO(001) buffer layers are investigated and compared to those grown on Cu/Si(001). The use of an Fe seed layer a few monolayers thick leads to the epitaxial growth of high surface quality Cu(001) buffer layers on MgO(001), while Cu growth on the bare MgO(001) substrate results in polycrystalline films. Magneto-optic Kerr effect magnetometry shows that Ni films grown on Cu/Fe/MgO(001) exhibit dominant perpendicular magnetic anisotropy up to ∼90 Å, which is similar to that of Ni films grown on Cu/Si(001). The polycrystalline Ni films also exhibit perpendicular magnetic remanence, but with a dominant in-plane magnetization component.

Magnetic domain confinement by anisotropy modulation

The spin configuration in a magnet is in general a "natural" consequence of both the intrinsic properties of the material and the sample dimensions. We demonstrate that this limitation can be overcome in a homogeneous ferromagnetic film by engineering an anisotropy contrast. Substrates with laterally modulated single-crystal and polycrystalline surface regions were used to induce selective epitaxial growth of a ferromagnetic Ni film. The resulting spatially varying magnetic anisotropy leads to regular perpendicular and in-plane magnetic domains, separated by a new type of magnetic wall---the "anisotropy constrained" magnetic wall.

Spin-engineering magnetic media

The explosion in demand for increased data-storage density is driving the exploration of new magnetic media. Here we describe a new type of magnetic medium in which the spin configurations are engineered in chemically homogeneous magnetic films: regularly arranged in-plane and out-of-plane spin configurations are defined by altering the magnetic anisotropy. These spin-engineered media not only maintain the surface planarity but also the homogeneity of the magnetic materials, and our method is likely to find immediate application on account of its simplicity and ease of integration.