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The effect of ion irradiation on the proximity effect in YBa2Cu3O7−δ/La0.67Sr0.33MnO3 and YBa2Cu3O7−δ/SrTiO3/La0.67Sr0.33MnO3 heterostructures has been investigated using spin-polarized neutron reflectivity experiments. We demonstrate that the magnetization in the ferromagnetic (La0.67Sr0.33MnO3) layer at the interface is correlated with the suppression of the superconductivity in the YBa2Cu3O7−δ layer after irradiation, while the layer structure of the heterostructures remains intact. The evolution of the magnetization of the interfacial ferromagnetic layer studied as a function of temperature for both the irradiated heterostructures shows the absence of the proximity effect observed in the un-irradiated samples. The absence of a proximity effect is attributed to the suppression of the superconductivity, as seen in macroscopic magnetization measurements of the heterostructures after ion irradiation. [ABSTRACT FROM AUTHOR]

Antiferromagnetic coupling between rare-earth (RE) and transition metals (TM) gives rise to various magnetic ground states in RE/TM heterostructures. Interface structure and morphology tend to play important roles in defining the magnetic properties of heterostructures of these materials. Using spin-dependent polarized neutron reflectivity (PNR), we found a distinct magnetic structure for RE/TM (Gd/Co) multilayers having different interface morphologies. Two Gd/Co multilayers, each consisting of eight bilayers of Gd and Co, were grown at different argon pressures to accomplish variation in the interface morphology. The Gd/Co multilayer, which is grown at a lower argon pressure, exhibits lower intermixing/interdiffusion at the interfaces and shows asymmetric magnetic hysteresis loops below the compensation temperature (Tcomp ∼ 140 K) and antisymmetric magnetoresistance at Tcomp. The other multilayer, grown at two different argon pressures for the top and bottom four bilayers, shows a double hysteresis loop with an exchange-bias-like shift to the field axis at temperatures above Tcomp (∼150 K). From PNR measurements across Tcomp, these behaviors were attributed to interface dependent magnetic helical structures. The PNR results indicate the formation of a twisted helical magnetic structure with planar 2π domain walls and the evolution of magnetic inhomogeneities below Tcomp. The interface dependent twisted helical magnetic structures and the development of highly correlated magnetic inhomogeneities may find applications in all-spin-based technologies. [ABSTRACT FROM AUTHOR]

We describe measurements of the uniaxial magnetic anisotropy and spin-flop rotation of the Néel vector in antiferromagnetic CuMnAs thin films using neutron diffraction. The suppression of the magnetic (100) peak under magnetic fields is observed for films as thin as 20 nm, indicating that they undergo a spin-flop transition. Good agreement is found between neutron diffraction and electrical transport measurements of the spin-flop rotation in the same layer with similar shape and hysteresis of the obtained curves, while the neutron measurements provide a quantitative determination of the spin flop extending throughout the antiferromagnet layer. [ABSTRACT FROM AUTHOR]

Collective behaviors in which the magnetic response depends not only on the individual constituents but also on their interactions are an area of active research. We have produced a paradigmatic system where DC magnetron sputtered FexAg100-x (x=15, 35) nanogranular films exhibit a crossover between a superspin glass (SSG) state and a superferromagnetism (SFM), where direct exchange interactions overcome the frustration. The systems have been studied by non-linear susceptibility (NLS) and small angle neutron scattering (SANS). The NLS measurements were carried out between 2 and 300K, in the absence of a biasing magnetic field, with frequencies spanning two decades. These measurements shed light on the complex nature of the interactions and the intricate relationship between direct exchange and long range magnetic interactions. The use of SANS allows us to estimate qualitatively the lengthscale of the magnetic correlations, and therefore identify a clear difference between the collective "supermagnetic" states (i.e., SSG and SFM) while establishing links between the structure and the magnetic interactions. [ABSTRACT FROM AUTHOR]

We report on a study of ferromagnetic semiconductor (Ga,Mn)As/(Al,Ga,Mn)As bilayers using magnetometry and polarized neutron reflectivity (PNR). From depth-resolved characterization of the magnetic structure obtained by PNR, we concluded that the (Ga,Mn)As and (Al,Ga,Mn)As layers have in-plane and perpendicular-to-plane magnetic easy axes, respectively, with weak interlayer coupling. Therefore, the layer magnetizations align perpendicular to each other under low magnetic fields and parallel at high fields. [ABSTRACT FROM AUTHOR]

We present magnetometry data for a range of Fe thicknesses grown on GaAs and InAs substrates in order to determine the factors governing the evolution of the magnetic moment of epitaxial Fe grown on a zinc-blende semiconductor. Fe films grown at room temperature by molecular beam epitaxy were characterized structurally and magnetically. The estimated roughness amplitudes were 0.3 [+ or -] 0.2 nm for the Fe/GaAs interface and 0.6 [+ or -] 0.2 nm for Fe/InAs. We observe a greater reduction of the Fe magnetic moment for films grown on InAs as compared to GaAs, as the Fe films reach a bulk-like moment (within 10% deviation) at a thickness of ~5.2 nm and ~2.2 nm, respectively. We conclude that the growth conditions, in particular interface and interdiffusion effects, are the dominant mechanisms influencing the value of the magnetic moment for ultrathin Fe films on GaAs and InAs. Index Terms--Fe, interface magnetism, magnetic moment, magnetic thin films, polarized neutron reflectometry (PNR).

Research into interdiffusion and intermixing in Fe/Si trilayers produced with ions of different energies is presented. Clearly defined crystalline layers were seen in transmission electron microscopy cross sections of thicker films produced at the same ion energies, while the presence of FeSi (Fersilicite) was found from the diffraction patterns.

A simple domain model relates the observed scattering to the domain correlation length and the magnetic disorder. The results suggest that it is in the in-plane domain distribution rather than uniformly magnetized layers with structurally rough interfaces that gives rise to the diffuse intensity.

We report on x-ray and neutron scattering studies that reveal the structure of interfaces of C60 layers with adjacent transition metal layers, in this instance, Cu. Such interfaces produce room-temperature long-range spin order that is not described by conventional theories of metallic magnetism. We use a combination of hard x-ray reflectivity and neutron scattering to investigate the interfacial structure of two C60/Cu layered samples: a superlattice with multiple C60/Cu repeats and a simpler tri-layer structure. For both structures, we develop a consistent structural model for the two scattering techniques, which details the critical interfacial roughness between the layers. We find that while x-ray reflectivity provides a strong contrast between the C60 and Cu layers, the similar neutron scattering length density of the two materials severely reduces the neutron scattering contrast. Our results can be used to design material systems that permit studies of the magnetism of the C60/transition metal interfaces with spin-sensitive scattering probes such as polarized neutron reflectometry. [ABSTRACT FROM AUTHOR]

Using spin-polarized neutron reflectivity experiments, we demonstrate an unusual proximity behavior when a superconductor (SC) and a ferromagnet (FM) are coupled through an insulator (I) in YBa2Cu3O7−δ (SC)/SrTiO3 (I)/La0.67Sr0.33MnO3 (FM) heterostructures. We have observed an unexpected magnetic reversal confined to the interface region of the FM below the superconducting transition temperature. The magnetization of the interfacial FM layer at the I/FM interface was found to be aligned opposite to the magnetization of the rest of the FM layer. This result indicates that the Cooper pairs tunnel across the insulator, interact with the local magnetization in the interfacial region (extending ∼30 Å) of the FM, and then modify the magnetization at the interface. This unexpected magnetic behavior cannot be explained on the basis of the existing theoretical models. However, the length scale associated here clearly suggests the long-range proximity effect as a result of tunneling of Cooper pairs. The magnetic exchange field-effect across SC/I/FM interfaces driven by tunneling may serve as the basis for application in superconducting spintronic devices. [ABSTRACT FROM AUTHOR]

The surface, interface and element specificity of x-ray resonant magnetic scattering in combination with x-ray magnetic circular dichroism are used for spatially resolving the polarization and the spin accumulation in Mn high susceptibility material in close proximity to a ferromagnetic layer. The size of the Mn and Cu [L.sub.2-3]-edge dichroism has shown a decrease in the polarization for increasing copper thickness indicating the dominant interfacial nature of the Cu and Mn spin polarization.

Self-assembled arrays of nanospheres are used for patterning a Co/Pt multilayer into nanopillars. Soft x-ray magnetic scattering has helped in understanding the correlation between magnetic roughness and structural roughness and also in obtaining selective magnetometry of various magnetic elements.

The effects of the AlO(sub x) barrier layer on the magnetic moment of Fe are studied using polarized neutron reflection. The sample having nominal composition 25 nm Au/5 nm Fe/1.3 nm AlO (sub x)/GaAs(001) concludes that there is no dead layer at the AlO (sub x) interface.

Off-specular polarized neutron reflectivity is used to probe a Co/Pt multilayer that is magnetically patterned using ion irradiation through a stencil. Both specular and off-specular measurements indicate the formation of an artificial magnetic domain structure when the sample is in its remanent state.

As-quenched and nanocryatallized structures for Nb-poor Fe-Nb-B(-P-Cu) alloys melt spun in air are discussed. This indicates that the precursor to the uniform nanostructure with high u(sub e) is not always a fully amorphous phase.

Results obtained from a multilayer through resonant magnetic scattering performed on the XMaS beamline at the European Synchrotron radiation facility are discussed. High-quality U/Fe multilayer through dc sputtering was produced.

Effect of other solid solution buffer layers (BLs) on metallurgical microstructure and giant magnetoresistance (GMR) of Co/Cu multilayers fabricated on them is discussed. A guiding principle for the material research for BLs to realize flat interfaces with large lateral grain size in the multilayers was detected.

Resonant magnetic x-ray scattering with off-specular neutron studies from magnetron-sputtered Co/Cu and Co/Ru multilayers grown at the second antiferromagnetic coupling peak is discussed. Ratio of the magnetic to structural correlations length is dependent on the magnitude of the exchange coupling and ranges from 0.4 to 1.4.

Using the newly emerged theory model of an electromagnetic proximity effect, we demonstrate that it provides a good description of our previously reported anomalous Meissner screening observed in thin film superconductor-ferromagnet proximity structures. Using the low energy muon spin rotation measurement technique, we further investigate this new theory by probing directly the flux screening in various superconductor-ferromagnet proximity structures. We examine its main characteristics and find in general good agreement between theory and experiment. Understanding and control of this new proximity effect is an important step forward toward a new generation of superconducting spintronic devices. [ABSTRACT FROM AUTHOR]

We determine layer selectively the magnetic moments, spin orientations and thicknessess of an epitaxial double spin valve structure, Si(001)/Cu/FeNi/Cu /Co/Cu/FeNi/Cu, using Polarised Neutron Reflectivity (PNR). At saturation, the layer-averaged magnetic moment per Co atom was found to be 1.71 [+ or -] 0.08 [[micro].sub.B], while the top (bottom) FeNi layer moment was 1.08 [+ or -] 0.06 [[micro].sub.B] (0.95 [+ or -] 0.08 [[micro].sub.B]). For an applied field strength [H.sub.a] smaller than the Co layer coercive field of ~100 Oe, the Co and FeNi layer magnetisation vectors are found to lie in-plane but canted with respect to each other in contrast to the fully antiparallel state predicted by simple energy minimisation. The observed canting is discussed with regard to the role of magnetic domains in the Co layer. Index Terms -- Magnetic films and multilayers, Polarised Neutron Reflectivity.

Inserting an antiferromagnetic layer of NiO between Pt and Y3Fe5O12 (YIG) changes the positive sign of the spin Hall magnetoresistance (SMR) in Pt/YIG to a negative sign at low temperature. Here, we use polarized neutron reflectometry to explore the coupling between NiO and YIG to understand the mechanism of the negative SMR. A weak uncompensated magnetic moment is observed in the NiO and the direction of this moment is perpendicular to YIG. Therefore, we infer that the spin axis of NiO is perpendicular to YIG. This result directly supports the explanation that the negative SMR results from the pure spin current reflected back by the NiO layer and the spin-flop coupling between NiO and YIG. [ABSTRACT FROM AUTHOR]

We report results on the effect of the AlOx barrier layer on the magnetic moment of Fe using polarized neutron reflection. The sample has nominal composition 25 nm Au/5 nm Fe/ 1.3 nm AlOx /GaAs(001). The metal deposition was done in ultrahigh vacuum and the Al oxidation was performed in two steps. From the fit to the neutron data we obtain for the magnetic moment of Fe the value (2.164±0.026)μB, very close to the bulk value (2.185μB at room temperature). We conclude that there is no dead layer at the AlOx interface. [ABSTRACT FROM AUTHOR]

We have investigated the magnetic properties of a Cu capped thin film of magnetite (Fe[SUB3]O[SUB4]) grown epitaxially on Pt(111). Conversion electron Mössbauer spectroscopy data show good agreement with those from bulk Fe[SUB3]O[SUB4], evidencing a good degree of structural order. The data point to in-plane ferrimagnetic alignment of the magnetic moment in the Fe[SUB3]O[SUB4] layer. Polarized neutron reflectivity (PNR) data determines the layer thinknesses to be 53±6 A˚ for the magnetite film and 106±5 A˚ for the Cu capping layer. The average magnetic moment determined by PNR for the Fe[SUB3]O[SUB4] layer is 2.8±0.3 μ[SUBB], smaller than the value of 4.1 μ[SUBB] for bulk Fe[SUB3]O[SUB4]. It is suggested that the reduced moment is in part a result of a reduced ordering temperature in the ultrathin film. [ABSTRACT FROM AUTHOR]

The effects of high-temperature annealing on ferromagnetic Co-doped Indium Tin Oxide (ITO) thin films have been investigated using X-ray diffraction (XRD), magnetometry, and X-Ray Magnetic Circular Dichroism (XMCD). Following annealing, the magnetometry results indicate the formation of Co clusters with a significant increase in the saturation magnetization of the thin films arising from defects introduced during cluster formation. However, sum rule analysis of the element-specific XMCD results shows that the magnetic moment at the Co sites is reduced after annealing. The effects of annealing demonstrate that the ferromagnetism observed in the as-deposited Co-doped ITO films arises from intrinsic defects and cannot be related to the segregation of metallic Co clusters. [ABSTRACT FROM AUTHOR]