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Structural, magnetic, and superconducting properties of ferromagnetic/superconducting multilayers of Fe4N/NbN are examined. The onset of superconductivity occurs at NbN layer thickness of ∼100 A. Below this thickness ferromagnetism of the Fe4N layers is observed. Above this thickness superconductivity of the NbN is also observed, but there is no evidence for interlayer magnetic or superconductive coupling. The results are used in the formulation of guidelines for future searches of novel interlayer coupling phenomena. The superconducting critical field curves are reasonably well described within the framework of the theory for ferromagnetic/superconducting multilayers.

We examine structural, magnetic, and superconducting properties of magnetic/superconducting Ni/Nb multilayers. The Ni(Nb) films are textured {111}({110}) and have smooth interfaces. The average moment of the Ni atoms in the structure drops by 80% from that of bulk Ni for 19 A thick Ni layers in proximity to 140 A thick Nb layers, and goes to zero for smaller Ni thicknesses. The Nb layer is not superconducting for thicknesses

The authors present magnetic characterization of epitaxial Fe/Cr(211) and Fe/Cr(100) superlattices grown simultaneously on MgO(110) and (100) substrates, respectively. At room temperature, the coupling for these two orientations oscillates in sign with the same period (18{angstrom}), phase and strength. These results indicate that the long-period oscillation is independent of the nested feature of the Cr Fermi-surface. They examine the temperature dependence of interlayer coupling and find a uniform AF bias develops in the (211) samples upon cooling and observe strongly temperature-dependent biquadratic coupling in the (100) samples.

Quantum confinement is studied with angle-resolved photoemission for ultrathin Cu separated from the Cu(100) substrate by an epitaxial wedge of Co (0--11 A) that serves as a finite barrier. For 2 ML of Cu, the photoemission intensities of the Cu [ital sp] quantum-well (QW) state at 1.6 eV binding energy and the corresponding [ital d]-band-derived QW state at 2.4 eV increase rapidly with the thickness of the Co barrier and indicate stronger confinement of the [ital d] QW state than of the [ital sp] state. Implications for the magnetic coupling and magnetoresistance are discussed.

We demonstrate epitaxial growth of the bcc transition metals Nb, Mo, Fe, and Cr via sputtering onto single crystal MgO substrates. The epitaxial growth orientations are (011), (112), and (001) when grown onto MgO (111), (011), and (001), respectively. Further, we demonstrate that, under appropriate growth conditions, superlattices of these materials (e.g., Fe/Cr, Fe/V, and Mo/V) can be grown with the same epitaxial order as the films.

Sputtered Fe/FeSi films possessing antiferromagnetic (AF) interlayer coupling at room temperature develop ferromagnetic remanence when cooled below 100 K, but the AF coupling can be restored at low temperature by exposure to visible light of sufficient intensity (≳10 mW/mm2). We attribute these effects to charge carriers in the FeSi spacer layer, which, when thermally or photogenerated, are capable of communicating spin information between the Fe layers.

We report experimental and theoretical studies of the magnetization curves of Fe/Cr(211) superlattices with antiferromagnetic interlayer coupling and uniaxial in-plane anisotropy. There are substantial differences between structures with an even and an odd number of Fe layers, when the magnetic field is applied along the easy axis. For even layered superlattices, the inequivalence of the terminal Fe layers gives rise to a surface spin-flop transition that evolves into a bulk spin-flop arrangement with increasing magnetic field, as originally envisioned by Keffer and Chow [Phys. Rev. Lett. 31, 1061 (1973)].

A epitaxial orientation of Fe/Cr superlattices---Fe/Cr(211) on MgO(110)---is grown by magnetron sputtering. Its structural and magnetic characterizations are presented and compared to those for Fe/Cr(100) superlattices grown simultaneously onto MgO(100) substrates. The epitaxial orientation of the Fe/Cr(211) superlattices is Fe/Cr[01\ifmmode\bar\else\textasciimacron\fi{}1]\ensuremath{\parallel}MgO[001] and Fe/Cr[1\ifmmode\bar\else\textasciimacron\fi{}11]\ensuremath{\parallel}MgO[11\ifmmode\bar\else\textasciimacron\fi{}0], while that for Fe/Cr(100) is Fe/Cr[001]\ensuremath{\parallel} MgO[011]. A uniaxial, in-plane surface anisotropy for the Fe/Cr(211) superlattices along the Fe[01\ifmmode\bar\else\textasciimacron\fi{}1] of 0.06 erg/${\mathrm{cm}}^{2}$ is obtained from analysis of the magnetization hysteresis loops. Four oscillations in the antiferromagnetic interlayer coupling and giant magnetoresistance (GMR) are observed with a period of 18 \AA{} for both orientations. The strength, oscillation period, and phase of the magnetic coupling are identical for the two orientations. The GMR values increase by a factor of \ensuremath{\sim}4 to 5 on cooling from room temperature to 4.2 K. At 4.2 K the maximum GMR value of the [Fe(14 \AA{})/Cr(8 \AA{})${]}_{50}$ superlattice is 70% for the (211) orientation and 150% for the (100) orientation.

We have fabricated a thin film magnetic system consisting of nanoscale Mn11Ge8 ferromagnetic clusters embedded in a MnxGe1−x dilute ferromagnetic semiconductor matrix. The clusters form for growth temperatures of ∼300 °C with an average diameter and spacing of 100 and 150 nm, respectively. While the clusters dominate the magnetic properties, the matrix plays a subtle but interesting role in determining the transport properties. Variable range hopping at low temperatures involves both nanoclusters and MnGe sites, and is accompanied by a negative magnetoresistance attributed in part to spin-dependent scattering analogous to metallic granular systems.

We report on the epitaxial growth of a group-IV ferromagnetic semiconductor, Mn(x)Ge(1-x), in which the Curie temperature is found to increase linearly with manganese (Mn) concentration from 25 to 116 kelvin. The p-type semiconducting character and hole-mediated exchange permit control of ferromagnetic order through application of a +/-0.5-volt gate voltage, a value compatible with present microelectronic technology. Total-energy calculations within density-functional theory show that the magnetically ordered phase arises from a long-range ferromagnetic interaction that dominates a short-range antiferromagnetic interaction. Calculated spin interactions and percolation theory predict transition temperatures larger than measured, consistent with the observed suppression of magnetically active Mn atoms and hole concentration.

A series of sputtered Fe(30{Angstrom})/Si(x) superlattices were grown for x=10--40{Angstrom}. Magnetization and Kerr hysteresis loops, and neutron-reflectively measurements identify antiferromagnetic (AF) coupling of the Fe layers at room temperature for x=15{Angstrom} nominal thickness, with switching fields of 6kOe. X-ray structural analysis indicate that the spacer medium is crystalline for x

Magnetoresistance measurements are used to identify the spin-flip transition temperature Tsf in 500 and 3000 A thick Cr(001) films grown epitaxially on LiF(001). Tsf is suppressed to a lower temperature in the 500 A film compared to the bulk value of 123 K. The shift in Tsf with film thickness follows a similar stress dependence as that reported previously for bulk Cr crystals. The magnetoresistance is 50% at 4.2 K in a field of 5 T and still shows no sign of approaching saturation.

We report magnetothermopower S(H) measurements at room temperature for sputtered [Fe(32 A) / Cr(x)]30 superlattices with x ≈ 5–50 A. The thermopower in zero field S(H = 0) appears to extrapolate to the known values for Fe and Cr in the x = 0 and large-x limits, respectively, and drops below these values at intermediate x. S follows the same trend with H and x as the magnetoresistance (MR), which shows oscillatory behavior as a function of x, and large field effects for antiferromagnetic Fe interlayer couplings. Both S(H) and the MR saturate when the applied field aligns the magnetization of the Fe-layers parallel to each other, but the thermopower is enhanced by application of a magnetic field, while the resistivity decreases, in accord with expectation.

The modulation wavelength dependence of the surface‐wave velocity in Cu/Ni superlattices has been investigated using Brillouin scattering. It is the first compositionally modulated system to be studied by this technique and the first for which elastic properties have been determined by both ‘‘macroscopic’’ methods and Brillouin scattering. Contrary to the enhancements previously reported in the biaxial modulus and in the Young’s modulus, the modulus associated with the surface‐wave velocity shows no evidence of anomalous behavior.

Angle-resolved-photoemission studies of the dispersion of the quantum-well states in copper thin films deposited on a Co(001) substrate reveal that hybridization in the interface leads to a large increase in the effective mass of the electrons. These observations have implications for theories of the oscillatory exchange coupling in the related magnetic multilayers, particularly where Fermi-surface spanning vectors away from the center of the zone are invoked as in the case of the short-period oscillation in the Co/Cu(001) multilayers.

We present structural and magnetic characterization of epitaxial Fe/Cr(211) and Fe/Cr(100) superlattices grown simultaneously on MgO(110) and MgO(100) substrates by magnetron sputtering. The epitaxial orientation of the Fe/Cr(211) superlattice with the MgO(110) substrate is Fe/Cr[011]//MgO[001] and the orientation of Fe/Cr(100) is Fe/Cr[001]//MgO[011]. We find that for both orientations, that the interlayer coupling oscillates in sign with a period of 18 A, and, furthermore, that the strength and phase of the magnetic coupling are also nearly identical for these two orientations.

We report the epitaxial growth of CdCr2Se4, an n-type ferromagnetic semiconductor, on both GaAs and GaP(001) substrates, and describe the structural, magnetic and electronic properties. Magnetometry data confirm ferromagnetic order with a Curie temperature of 130 K, as in the bulk material. The magnetization exhibits hysteretic behavior with significant remanence, and an in-plane easy axis with a coercive field of ~125 Oe. Temperature dependent transport data show that the films are semiconducting in character and n-type as grown, with room temperature carrier concentrations of n ~ 1 x 10^18 cm-3., 12 pages, 3 figures

In a well-known advertising campaign, respondents asked to spell "relief" invariably spelled the name of a popular antacid. Three decades ago, an American nurse working in Sweden found less unanimity, however, when it came to the spelling of "pain." Intrigued by the clear distinction that her patients made between pain and ache, Fannie Gaston-Johansson wanted to know more. Did the same differentiation transcend cultural and linguistic divides? Was it possible to develop a simple, word-based tool to reliably quantify pain? Her search for these and other answers would result in outstanding scholarship, a patented invention and history-making achievement.

We report the epitaxial growth of Fe/Cr(100) superlattices onto MgO(100) single‐crystal substrates by magnetron sputtering. Superlattices that are epitaxially oriented within 1° both in‐plane and out‐of‐plane with the MgO substrate are achieved by initial growth of a Cr base layer at high temperature. Multiple superlattice diffraction peaks are observed in the low‐ and high‐angle x‐ray diffraction spectra. Three peaks are observed in the magnetoresistance associated with the oscillatory antiferromagnetic interlayer magnetic coupling as a function of Cr thickness. A maximum magnetoresistance of 150% at 4.2 K (28% at room temperature) is observed for a Cr(100 A)/[Fe(14 A)/Cr(8 A)]50 superlattice.

The saturation field of sputtered Fe/Nb superlattices oscillates as a function of the Nb thickness with a periodicity of ∼9 A. In contrast to the case of Fe/Cr superlattices, the concurrent magnetoresistance oscillations were found to be very weak. Yet polarized neutron reflection measurements confirm that the Fe/Nb superlattices with high saturation field possess a magnetic ground state of the +−+− type. Neutron and x‐ray measurements indicate that, while the crystalline and antiferromagnetic order is well developed along the thickness of the film, the average lateral size of the crystallites (as well as of the magnetic domains) is quite small. This effect (thought to be related to the gross mismatch of the iron and the niobium crystal lattices) may be the cause of the high overall resistance of the material, and its weak dependence on the magnetization.

Sputtered Fe/Si superlattices were grown to study the magnetic coupling between ferromagnetic Fe layers (30 A thick) for Si spacer‐layer thicknesses (tSi) between 10 and 40 A. The material is ferromagnetical for tSi≤13 A and antiferromagnetically coupled for 13 A≤tSi≤17 A. For tSi≥17 A the Fe layers are uncoupled. X‐ray analysis indicates that the system is well layered, but that the crystal structure remains coherent only for tSi≤17 A. These results, along with our Mossbauer investigation, strongly suggest that the Si layer is crystalline for tSi≤17 A, and is silicide in nature. For thicker spacers, Si becomes amorphous. We propose a model of the layering that is consistent with the known properties of Fe silicide.

Sputtered Fe/Mo superlattices grown on sapphire exhibit an oscillatory magnetic coupling as a function of Mo thickness. Ferromagnetic Fe layers 25 A thick couple across the nonmagnetic Mo layers ferro‐ or antiferromagnetically with a period of ∼11 A Mo. Ferromagnetically aligned films show the anticipated trend in longitudinal Kerr‐rotation values based on calculation, while the antiferromagnetically coupled films in zero field yield only weak Kerr signals due to their characteristically ‘‘pinched’’ hysteresis loops. The films are well ordered and exhibit up to seven low‐angle, x‐ray diffraction peaks, but have negative magnetoresistive anomalies that are only ≲2% at 4.2 K.

We report the results of transport measurements on epitaxial Cr thin films. The variation of TN (The Neel transition temperature) with respect to the film thickness is discussed in terms of the stress in the film. In addition, the temperature dependence of the magnetoresistance and Hall resistance for temperatures from 4 to 150 K are measured and discussed, with particular attention to the temperature dependence of the nonlinear portion of the Hall data.

Magnons in Cu Ni Superlattices have been investigated using Brillouin scattering. Although the results indicate that the magnon is in the range between that expected for an alloy and a superlattice with sharp interfaces, the very broad measured line widths make a quantitative conclusion impossible.

The Raman-active transverse-optic (TO) phonon mode of Ru was measured in a series of Co/Ru superlattices. The changes in the frequency of the TO vibration, interpreted within the framework of confined phonons, are in excellent agreement with published dispersion curves for bulk Ru obtained from inelastic neutron-scattering experiments. Interpretations of the frequency shifts of the Ru TO mode as due to phonon-folding or lattice-strain effects are ruled out by the data. {copyright} {ital 1996 The American Physical Society.}

We report photoinduced antiferromagnetic (AF) interlayer coupling in sputtered Fe/(Fe-Si) superlattices. The superlattices are intrinsically AF coupled at room temperature and become increasingly ferromagnetically coupled when cooled below 100 K, but the AF coupling is restored at low temperature by exposure to visible light of sufficient intensity ([gt]10 mW/mm[sup 2]). These effects are due to charge carriers in the Fe-Si spacer layer which, when thermally or optically generated, are capable of communicating spin information between the Fe layers.

Sputtered Fe(20 A)/Nb superlattices were prepared with Nb thicknesses ranging from {similar to}2 to 40 A, and oscillatory interlayer magnetic coupling was observed by means of magnetoresistance (MR), magnetometry, and Kerr rotation measurements. As many as five oscillations between ferromagnetic and antiferromagnetic coupling were observed at room temperature with a Nb periodicity of {similar to}9 A. The largest negative MR measured, however, was only 0.3%. The low MR values of high resistivity (60--120 {mu}{Omega} cm) suggest that the structural disorder associated with the lattice mismatch (13% in this system) plays an important role in governing the transport phenomenon.

A Heisenberg model is solved for the coupling of two-dimensional ferromagnetic layers separated by nonmagnetic spacer layers in a superlattice configuration. The cases of noncoupling, and ferromagnetic and anti-ferromagnetic interlayer couplings, are solved for the temperature dependence of the magnetization at low temperature; the results yield linear, ${\mathit{T}}^{3/2}$ and ${\mathit{T}}^{2}$ power laws, respectively. Experimental realization of the coupling cases was then sought. Three sputtered Fe/Cr superlattices with 10 \AA{} Fe layers and Cr-layer thicknesses of 100, 20, and 10 \AA{} were chosen to span the three cases, respectively. Superconducting-quantum-interference-device magnetometry yields linear and ${\mathit{T}}^{3/2}$ behavior for the first two cases. M\"ossbauer spectroscopy in zero field indicates an approximately ${\mathit{T}}^{2}$ behavior for the antiferromagnetically coupled sample. The results are discussed and related to recent magnetotransport work.

The temperature dependence of the resistivity of three sputtered Fe/Cr superlattices was analyzed. Two are antiferromagnetic and one is ferromagnetic. Also, a series of Fe/Cr superlattices was characterized as a function of Cr thickness by means of resistivity, Kerr-rotation, and x-ray-diffraction measurements. Magnetoresistance measurements for films with 32-\AA{} Fe layers confirm the presence of three oscillations with peaks at \ensuremath{\sim}11, 27, and 42 \AA{} Cr. The Kerr-rotation measurements for fixed Fe thicknesses of 15, 25, 32 and 40 \AA{} indicate that the first antiferromagnetic region is always between \ensuremath{\sim}6 and 17 \AA{} Cr thickness. The low-angle x-ray results show that the structure is not ideal, based on comparison to dynamical simulation or to the quality of similarly prepared Fe/Mo superlattices. The magnetoresistivity of the antiferromagnetic films decays from its maximum value at low temperature with a ${\mathit{T}}^{2}$ behavior below \ensuremath{\sim}100 K, while a ferromagnetic film could be similarly approximated by a ${\mathit{T}}^{3/2}$ behavior. These power laws are a consequence of the thermal excitation of magnons in these anisotropic antiferromagnetic and ferromagnetic superlattices, respectively. The resistivities due to sd-interband scattering ${\mathrm{\ensuremath{\rho}}}_{\mathit{s}\mathit{d}}$ are approximated by a ${\mathit{T}}^{2}$ behavior and roughly a ${\mathit{T}}^{3}$ behavior, respectively. This indicates that for the antiferromagnetic films the dominant contributions to ${\mathrm{\ensuremath{\rho}}}_{\mathit{s}\mathit{d}}$ come from processes mediated by magnons as well as phonons.

A polarimeter for x-ray and vacuum ultraviolet (XUV) radiation was built to measure the spatial and spectral dependence of the polarization of the light produced by the new undulator at the U5 beamline at NSLS. The fourth-harmonic radiation was measured, and it does not agree with predictions based on ideal simulation codes in the far-field approximation.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The elastic and structural properties of Cu/Pd and Cu/Ni superlattices have been determined. Microstructurally the films have the same growth mechanisms, growth textures, and composition modulation amplitudes, as in past studies where the ``supermodulus effect'' was reported. Advanced techniques have been used to measure the flexural, shear, and Young's moduli of the thin films, and no significant anomalous elastic behavior has been observed.

We report giant magnetoresistance (GMR) as high as 150% at 4.2 K in epitaxial Fe/Cr superlattices. Samples prepared by magnetron sputtering on MgO(100) produced the expected Fe/Cr(100) orientation; however, deposition on MgO(110) produced a novel (211) low‐miller‐index orientation. The crystallographic orientations and superlattice nature of the samples were confirmed by both low‐ and high‐angle x‐ray diffraction. The Fe/Cr(211) superlattices have an in‐plane uniaxial anisotropy (KU=9×105 ergs/cm3) along the Fe[011] which give the sample a rich magnetic behavior. The GMR with the current along the [011] is ≊20% higher than that along the [111] direction of the (211) plane. The GMR for the (211) superlattices shows four oscillations with Cr thickness. Both orientations shows the expected long‐period oscillation of 18 A Cr and a GMR increase by a factor a 4 when cooled from room temperature to 4.2 K.