B. Kardasz

Enhanced spin pumping at yttrium iron garnet/Au interfaces

Spin injection across the ferrimagnetic insulator yttrium iron garnet (YIG)/normal metal Au interface was studied using ferromagnetic resonance. The spin mixing conductance was determined by comparing the Gilbert damping parameter α in YIG/Au and YIG/Au/Fe heterostructures. The main purpose of this study was to correlate the spin pumping efficiency with chemical modifications of the YIG film surface using in situ etching and deposition techniques. By means of Ar+ ion beam etching, one is able to increase the spin mixing conductance at the YIG/Au interface by a factor of 5 compared to the untreated YIG/Au interface.

Exchange stiffness in thin film Co alloys

The exchange stiffness (A(ex)) is one of the key parameters controlling magnetization reversal in magnetic materials. We used a method based on the spin spiral formation in two ferromagnetic films ...

A method for measuring exchange stiffness in ferromagnetic films

An exchange stiffness, A(ex), in ferromagnetic films is obtained by fitting the M(H) dependence of two ferromagnetic layers antiferromagnetically coupled across a nonmagnetic spacer layer with a si ...

Spin current studies in Fe∕Ag,Au∕Fe by ferromagnetic resonance and time-resolved magneto-optics

A precessing magnetization within a magnetic double layer acts as a peristaltic spin pump which transports spin momentum but no net electric charge. Crystalline Fe single layers Au∕12Fe∕GaAs(001) and double layers Fe12∕(Au,Ag)∕Fe16∕GaAs(001) were prepared by molecular beam epitaxy, where the integers represent the number of Fe atomic layers, and (Au,Ag) represents a set of gold and silver layers of different thicknesses. Ferromagnetic resonance (FMR) was used to investigate spin diffusion in thick Au layers in Au∕12Fe∕GaAs(001) samples. Time-resolved magneto-optical Kerr effect (TRMOKE) measurements are an ideal tool for investigating the propagation of spin currents in these structures. Spin currents generated by the bottom 16Fe layer propagated across the normal metal spacer and resulted in rf excitations in the top 12Fe film. Landau-Lifshitz-Gilbert equations of motion modified by spin pump and spin sink effects were used to interpret the FMR and TRMOKE measurements. The spin diffusion lengths in Au we...

Structural and magnetic properties of NiMnSb/InGaAs/InP(001)

The structural and magnetic properties of NiMnSb films, 5–120 nm thick, grown on InGaAs/InP(001) substrates by molecular-beam epitaxy, were studied by x-ray diffraction, transmission electron microscopy (TEM), and ferromagnetic resonance (FMR) techniques. X-ray diffraction and TEM studies show that the NiMnSb films had the expected half-Heusler structure, and films up to 120 nm were pseudomorphically strained at the interface, greater than the critical thickness for this system, about 70 nm (0.6% mismatch to InP). No interfacial misfit dislocations were detected up to 85 nm, however, relaxation in the surface regions of films thicker than 40 nm was evident in x-ray reciprocal space maps. TEM investigations show that bulk, planar defects are present beginning in the thinnest film (10 nm). Their density remains constant but they gradually increase in size with increasing film thickness. By 40 nm these defects have overlapped to form a quasicontinuous network aligned closely with ⟨100⟩ in-plane directions. T...

Spin dynamics and magnetic anisotropies at the Fe/GaAs(001) interface

20Au/(d)Fe/GaAs(001) structures were deposited using molecular beam epitaxy, where Fe thickness d = (5...90) atomic layers. Interface anisotropies were investigated using the in-plane angular dependence of ferromagnetic resonance (FMR). Intrinsic and extrinsic contributions to magnetic damping were investigated using FMR linewidth (ΔH) measurements at 9, 24, 36, and 72 GHz (in-plane configuration) and 9, 24, and 36 GHz (perpendicular configuration). The in-plane cubic and uniaxial perpendicular anisotropies were well described by the bulk and interface contributions indicating that the Fe films have a high lattice coherence and high critical Curie temperature Tc. The in-plane uniaxial anisotropy is more complex and will be discussed in detail. The frequency dependence of ΔH(f) was analyzed using the Gilbert damping, two magnon scattering, and long range magnetic inhomogeneity contributions. The thickness dependence of the Gilbert damping parameter α was found to be well described by the bulk and interface...

Hyperfine fields in an Ag/Fe multilayer film investigated withL8iβ-detected NMR

Low energy

Interface atomic structure and magnetic anisotropy in ultrathin Fe films grown by thermal deposition and pulsed laser deposition on GaAs(001)

\beta

Magnetic anisotropies in GaAs/Fe(001) structures

-detected nuclear magnetic resonance (

Spin transport in Au films: An investigation by spin pumping

\beta