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Presents a study that examined thin epitaxial iron-cobalt alloy films sputtered on magnesium oxide substrates. Use of x-ray scattering and magneto-optical Kerr effect; Information on thin magnetic films; Structural properties of the iron compounds.

Presents a study which analyzed the structural properties of molecular beam epitaxy-grown thin cobalt (Co) films on sapphire substrates by high resolution x-ray scattering measurements. Regimes distinguished for the detailed analysis of the x-ray scattering cross-section; Description of the scattering methods; Outline of x-ray reflectivity and thin film Bragg scattering; Reflectivity measurements from Co films.

We report measurements of the magneto-optical Kerr effect (MOKE) on an optical grating of Ni-stripes on Si(111) and a grating of Al-stripes on a Ni thin film. The analysis of the MOKE signal at different orders of diffraction n reveals a change of the Kerr signal amplitude, which is periodic in n having the same periodicity as the total intensity of the diffracted light. For the grating of Ni-stripes we observe a definite change of the shape of the magnetic hysteresis loops also varying systematically with the order of diffraction n. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Evidence for a spin reorientation in antiferromagnetic (AFM) Mn2Au thin films induced by high magnetic fields as well as by the application of in-plane mechanical stress is provided. The AFM domain population in the samples was investigated by resonant X-ray Magnetic Linear Dichroism (XMLD) measurements at the L3 edge of Mn using a variable linear polarization of the incident photon beam. As grown samples show no XMLD signal due to averaging over a random AFM domain distribution. After the exposure to a 70 T in-plane magnetic field a clear XMLD signal indicating the generation of a preferential AFM domain orientation is obtained. The same type of XMLD signal is observed when the thin films are strained, demonstrating the feasibility of AFM domain manipulation by magnetic fields and stress in Mn2Au. [ABSTRACT FROM AUTHOR]

Presents a study that examined ferromagnetic resonance measurements on radio frequency sputtered cobalt-manganese multilayers. Use of ferromagnetic resonance and x-ray scattering; Background on thin and ultrathin magnetic layers.

We report on the fabrication and characterization of iron oxide nanoparticle thin film superlattices. The formation into different film morphologies is controlled by tuning the particle plus solvent-to-substrate interaction. It turns out that the wetting vs dewetting properties of the solvent before the self-assembly process during solvent evaporation plays a major role in determining the resulting film morphology. In addition to layerwise growth three-dimensional mesocrystalline growth is also evidenced. The understanding of the mechanisms ruling nanoparticle self-assembly represents an important step towards the fabrication of novel materials with tailored optical, magnetic or electrical transport properties. [ABSTRACT FROM AUTHOR]

We studied asymmetric superconducting spin valves with the layer sequence V/Fe/V/Fe/CoO, grown on MgO(100). These thin film heterostructures exhibit a superconducting spin valve (SSV) effect, that is, a difference, δTs, between the superconducting transition temperatures Ts with the magnetization directions of the two Fe layers oriented antiparallel and parallel. For pure Fe layers in the SSV we observe a maximum shift δTs = 24 mK. On replacing the Fe layers with FeV alloy layers, the SSV effect was increased to a maximum value of δTs = 35 mK. This is one of the largest shifts observed in SSV devices up to now, but still an order of magnitude smaller than the SSV effect observed in V layers grown on epitaxial Fe/V superlattices previously. Our results suggest a dominant importance of the Fe/V interface quality for the amplitude of the SSV effect. [ABSTRACT FROM AUTHOR]

Single-crystalline ZnO thin films have been grown on sapphire substrates and implanted by 40 keV Ni ions with a dose of 0.25-1.25×10 ions/cm. After implantation the samples have been annealed at T=1000°C for 30 minutes in air. Both as-prepared and annealed nickel-implanted ZnO samples have been investigated by ferromagnetic resonance (FMR), vibrating sample magnetometry (VSM), scanning electron microscopy (SEM), and optical techniques. SEM studies reveal that the surface of non-implanted ZnO thin film is very smooth, while microcracks are present in the Ni-implanted ZnO samples. Annealing after implantation recovers the surface of the implanted ZnO. Energy dispersive X-ray spectroscopy shows that the Ni concentration increases with increasing the implantation dose. Optical measurements of the Ni-implanted ZnO thin films indicate that annealing results in formation of a new phase. This phase is attributed to NiO that appears due to redistribution and oxidation of the implanted Ni ions in the ZnO matrix. Magnetic measurements show that both as-implanted and annealed samples exhibit room-temperature ferromagnetism. VSM data indicate that annealing procedure results in decreasing the magnetic moment per Ni atom and higher coercivity at low temperatures. Magnetic-resonance studies reveal highly anisotropic FMR signal in the as-implanted Ni:ZnO samples starting from the dose of 0.5×10 ions/cm. We also observe a step-wise increase of the effective magnetization at the dose of 1.0×10 ions/cm, which is explained by magnetic percolation of the Ni nanoparticles. Narrow resonance signals with unusual angular dependence are observed in magnetic-resonance studies of the annealed Ni:ZnO samples, which have been related to the formation of a system of non-percolated NiO-coated Ni nanoparticles as a result of annealing in air. We did not observe experimental evidence for intrinsic ferromagnetism in the Ni-implanted ZnO thin films. [ABSTRACT FROM AUTHOR]

Polarized neutron reflectivity has been used to investigate the peak pattern and the magnetization reversal process of laterally structured Fe- and CoFe-films. The peak pattern of the wire arrays was analyzed in the specular as well as in the off-specular regime. The intensities of the different cross-sections at the off-specular first-order peak were investigated as a function of external magnetic field. Magnetization reversals are discussed and compared to MOKE studies of the same system. [ABSTRACT FROM AUTHOR]

The ferromagnetic resonance and magnetization of single-crystal thin (27-100 Å films grown in the (110) direction are measured in the temperature range 20-400 K. The films are prepared by molecular-beam epitaxy on single-crystal sapphire Al[sub 2]O[sub 3](11&2macr;0) substrates with a Nb(110)buffer layer. The angular dependence of the parameters of the ferromagnetic resonance spectrum is observed to have a 180° character when the static magnetic field is rotated in the plane of the sample. It is established that this angular dependence can be described on the assumption that the lattice distortions are essentially trigonal. A comparative analysis of previous data for Fe(001) films with the data for Fe(110) films shows that the source of the corrections to the cubic anisotropy constant is the characteristic distribution of the strains along the thickness of the film. The ferromagnetic resonance and magnetization of single-crystal thin (27-100 Å films grown in the (110) direction are measured in the temperature range 20-400 K. The films are prepared by molecular-beam epitaxy on single-crystal sapphire Al[sub 2]O[sub 3](11&2macr;0) substrates with a Nb(110)buffer layer. The angular dependence of the parameters of the ferromagnetic resonance spectrum is observed to have a 180° character when the static magnetic field is rotated in the plane of the sample. It is established that this angular dependence can be described on the assumption that the lattice distortions are essentially trigonal. A comparative analysis of previous data for Fe(001) films with the data for Fe(110) films shows that the source of the corrections to the cubic anisotropy constant is the characteristic distribution of the strains along the thickness of the film. [ABSTRACT FROM AUTHOR]

An optimized heterostructure design and an optimized surface sputter-cleaning procedure allow the growth of high-quality epitaxial Fe(001) thin films at T[sub s] < ∼50°C on selectively doped GaAs/Al[sub 0.35]Ga[sub 0.65]As heterostructures, while retaining the high quality transport property of the two-dimensional electron gas. Magneto-optic Kerr effect measurements and model calculations indicate a dominant uniaxial in-plane anisotropy (easy axis along [110], hard axis along [1 - 10]) and small coercivity (∼15 Oe). Interface sensitive [sup 57]Fe Mössbauer measurements prove the absence of both magnetic "dead layers" and "half-magnetization" phases (compared to pure Fe), and provide evidence for intermixing within a few monolayers, retaining, however, a metallic Fe state and high Fe magnetic moments at the interface. [ABSTRACT FROM AUTHOR]

We have measured the thermal expansion between 20 and 450 °C of epitaxially grown GaAs thin films on Si(001) as well as of the Si substrate by means of high-resolution x-ray scattering. Our results show that the thermal expansion of GaAs in the direction parallel to the film plane follows the thermal expansion of the silicon substrate and is therefore smaller than in bulk GaAs. Furthermore, the thermal expansion perpendicular to the film plane (parallel to the growth direction) exceeds the bulk GaAs value by the Poisson contribution as a result of the in-plane constraint. The thermal expansion coefficients for GaAs films on Si(001) substrates in the directions parallel and perpendicular to the film plane are αT||(GaAs) =3.46×10-6/K and αT⊥(GaAs) =8.91×10-6/K, respectively. [ABSTRACT FROM AUTHOR]

Presents an abstract of the study 'Polarized Neuron Reflectivity Studies of Biquadratic Coupling in [Fe/Cr] (100) and [Fe/Al] (100) Superlattices and Films,' by J. F. Ankner, A. Schreyer et al., from a 1994 issue of the 'Journal of Applied Physics.'

We have studied the magnetotransport properties of thin films of the Heusler compounds Cu2MnAl Co2MnGe, and Co2MnSi prepared by sputtering on substrates at room temperature. By stepwise annealing at high temperatures, we transform the as-prepared, weakly magnetic, nanocrystalline state to the fully ordered, crystalline state via several intermediate steps. At the phase boundary between the nanocrystalline state and the long-range-ordered crystalline state, we observe a change of the electrical resistivity from that of a strongly disordered metal with negative dρ/dT to that of a normal metal with positive dρ/dT. The high-field magnetoresistance (MR) for Cu2MnAl is large, negative, and isotropic and is mainly due to static spin disorder scattering. For Co2MnGe and Co2MnSi a corresponding sizable spin disorder MR is missing. At low fields Co2MnGe and Co2MnSi exhibit a conventional anisotropic MR, whereas the low-field MR for Cu2MnAl is negative and isotropic. In the nanocrystalline phase of Co2MnGe and Co2MnSi we find a large anomalous Hall effect (AHE), which can be attributed to very effective skew scattering at the nanocrystalline grain boundaries. For Cu2MnAl, the AHE behavior is very unusual, indicating a situation with the contributions of spin-up and spin-down electrons to the anomalous Hall voltage nearly compensating each other. [ABSTRACT FROM AUTHOR]

Abstract: We have studied the superconducting proximity effect in thin film trilayer systems combining the ferromagnetic Heusler compound Co2MnGe with superconducting V. The thickness dependence of our Co2MnGe/V/ Co2MnGe trilayers with variable thicknesses of the V and the Co2MnGe layers is well described by the theoretical models developed by Radović and Tagirov. We determine a superconducting correlation length in the Co2MnGe layers of about 2.7 nm, which is exceptionally large when compared to other ferromagnets. We attribute this interesting feature to the spin glass type of magnetic order, which occurs in very thin layers of the Co2MnGe Heusler phase. [Copyright &y& Elsevier]

The use of hydrogen to modify the electronic structure in magnetic thin films and heterostructures has opened new routes to tailor magnetic interactions in materials. The presence of hydrogen modifies the electronic structure of the host. Hydrogen can therefore be used to control the strength and character of magnetic interactions. This effect can be used to change the coupling strength in thin films, as well as selectively altering one of the constituents in artificial heterostructures. For example, the switching from antiferromagnetic to ferromagnetic order, and vice versa, has been demonstrated for exchange coupled magnetic superlattices. As the sign of the interlayer exchange coupling J′ can be switched by the insertion of hydrogen, J′ arbitrarily close to zero must be accessible. When J′=0, the exchange interaction between adjacent magnetic layers is completely suppressed. The heterostructure can then be taken to consist of a collection of quasi two-dimensional magnetic sheets, when the ferromagnetic layers are very thin. Consequently, the introduction of hydrogen can be viewed as a route to tune the dimensionality of these structures. [Copyright &y& Elsevier]

Abstract: Magnetic soft X-ray scattering at the Ho M5 resonance was characterized using thin films, thus reducing the effect of the strong photon absorption. Magnetic scattering factors are found to be as large as at resonance, while the effective probing depth of the X-rays at the resonance maximum is of the order of 30Å at . The huge enhancement of magnetic scattering allows one to study ultrathin Ho films, which is exploited to investigate the thickness dependence of the Néel temperature in these long-period antiferromagnets. The tunable X-ray penetration depth across the resonance can be used for magnetic depth profiling, e.g. to study the depth-dependent growth of antiferromagnetic domains across the ferromagnetic/antiferromagnetic phase transition in Dy metal films. [Copyright &y& Elsevier]

Abstract: Spin-density wave state in thin Cr films is known to be under the influence of proximity effects from neighboring layers. In the present paper, we report on a combined neutron and X-ray scattering study of proximity effects in Cr/V films where the boundary conditions are due to V–Cr hybridization at interfaces. We provide evidence that the V/Cr interface has a strong and long-range influence on the global properties of the strain and spin-density waves in thin Cr films. [Copyright &y& Elsevier]