Adjacent Fe Layers Research Articles

Two oscillatory behaviors as functions of ferromagnetic layer thickness in Fe/Cr(100) multilayers

Oscillatory magnetoresistance as a function of the Fe layer thickness has been found in Fe/Cr(100) multilayers deposited on MgO(100). It is mainly attributed to an oscillatory interlayer exchange coupling between adjacent Fe layers as a function of the Fe layer thickness. Further, oscillatory variation of the saturation resistivity with Fe layer thickness was also observed. Both the oscillation periods are approximately 8 \AA{}. These two oscillations can be understood in terms of the partial confinement of the perpendicular motion to the layer plane of Fe majority spin electrons.

THEORETICAL CALCULATIONS OF THE RELATION BETWEEN THE GIANT MAGNETORESISTANCE IN Fe/Cr SUPERLATTICES

Based on the phenomenological theory of Camley and Barnas and coworkers (C-B), the dependence of magnetoresistance in Fe/Cr multilayers on the applied magne-tic field is calculated. In these multilayers an antiferromagnetic coupling exists between any two adjacent Fe-layers. The applied magnetic field is either parallel or perpendicular to the layers. Good agreement of the calculated results with the experimental ones is found. The symmetry implicitly involved in the C-B theory is disclosed and is used to simplify the original C-B formalism, this leads to the closed expressions for the distribution function of conducting electrons and for magnetore-sistance.

Brillouin scattering from spin waves in Fe/Cr multilayer films

Spin waves in two Fe/Cr multilayer films, one exhibiting ferromagnetic coupling and another antiferromagnetic coupling between adjacent Fe layers, have been studied by Brillouin scattering. Two bulk spin wave bands were observed for the antiferromagnetic film, but only one band for the ferromagnetic film.

Fermi-velocity effect on magnetoresistance in Fe/transition-metal multilayers

An effect of the Fermi velocity on the magnetoresistance is examined for Fe/Cr multilayers, based on a local-density electronic structure calculation. The Fermi velocity is remarkably enhanced by a change in the magnetic alignment of adjacent Fe layers from anti-parallel to parallel, leading to a significant amount of magnetoresistance.

Ferromagnetic resonance studies of (Ag/Fe)n multilayers (abstract)

We report a detailed ferromagnetic resonance (FMR) study, at X band, of magnetic films constituted of (Ag‖Fe multilayer‖Ag) sandwiches deposited by sputtering on heated mica substrates, where the base and the top Ag layers are 550 Å thick. For this (Ag/Fe) system the corresponding series of single Fe layers is reported in Ref. 1 (structural characteristics, FMR study). The resonance spectrum is studied as a function of the orientation [angle θH = (N̂,Ĥ) with respect to the film normal N̂] of the applied dc field H in a plane perpendicular to the film. We will present results relative to a series of Fe multilayers (Ag‖Fe)n=9, with spacer tAg=70 Å, corresponding to a set of individual Fe layer thicknesses (tFe=24, 36, and 48 Å). In summary, at room temperature, all the features (line shape, signal phase, position, linewidth) which characterize the resonance spectrum of a Fe multilayer are found different from the ones relative to the single resonance line observed for the corresponding single Fe layer (same tFe). More precisely, the angular variation of the resonance spectrum of the (tFe=24 Å) multilayer shows the presence of a unique line in the range (90°<θH ≲ 30) and then the splitting in two lines for θH ∈ (0°,30°), with Hres(θH) of the higher-field line following closely the single Fe layer Hres whereas the second line remains in low field (∼3.2 kOe). These observations provide evidence for the presence of a dynamical coupling between the precessing magnetizations of adjacent Fe layers. We suggest that the mechanism responsible for the Fe layers coupling is to be associated with the diffusion (or transport) of the microwave-induced magnetization of the conduction electrons of the whole metallic structure.

The growth of metastable bcc Cu(001) and lattice expanded Pd(001) and magnetic coupling in Fe/Cu/Fe and Fe/Pd/Fe trilayers

Bcc Cu(001) and laterally stretched Pd(001) can be grown epitaxially on Fe(001) and vice versa. FMR and BLS studies were carried out on Fe/Cu/Fe, Fe/Pd/Fe trilayers and Fe/Pd, Pd/Fe, Fe/Cu and Cu/Fe bilayers. The exchange coupling in bcc Cu was found to exhibit a behavior similar to bcc Cr but with a somewhat longer range of the antiferromagnetic interaction. 4 ML Pd couples Fe layers strongly ferromagnetically and is most likely ferromagnetically ordered. One additional Pd atomic layer destroys the long range order in Pd, but the Pd layer possesses fluctuating moments which are partly magnetized by the adjacent Fe layers. The exchange coupling in thick Pd interlayers ( > 8 ML) is weakly dependent on temperature and originated from a different mechanism.

Growth and magnetic studies of lattice expanded Pd in ultrathin Fe(001)/Pd(001)/Fe(001) structures.

Ultrathin Fe/Pd and Pd/Fe bilayers and Fe/Pd/Fe trilayers were studied using ferromagnetic resonance and Brillouin scattering. Pd interlayers always couple the Fe layers ferromagnetically. For thicknesses up to four monolayers the Pd is ferromagnetic, in agreement with theory. One additional atomic layer of Pd destroys the ferromagnetism, but the Pd still exhibits a fluctuating magnetic moment partly polarized by the exchange field from adjacent Fe layers. The magnetic moments in the interfaces were determined from the ferromagnetic-resonance absorption intensities

Evidence for Antiferromagnetic Coupling between Fe Layers through Cr from Neutron Diffraction

Small-angle neutron diffraction measurements have been made for a multilayer, [Fe(27 A)/Cr(12 A)]×30, at room temperature. It was found that the magnetizations of adjacent Fe layers are coupled in antiparallel. The decrease of antiferromagnetic peak intensity as a function of external field was observed. It is confirmed that the giant magnetoresistance in Fe/Cr multilayers is due to the antiferromagnetic ordering of Fe layers caused by the interlayer coupling across an intervening Cr layer.

Influence of Au and Ag at the interface of sputtered giant magnetoresistance Fe/Cr multilayers

Multilayer films consisting of 20-AA Fe and 15-AA Cr with amounts of Au and Ag varying from 0 to 4 AA deposited at alternate Fe/Cr interfaces have been RF-diode-sputtered, and their magnetic and magnetotransport properties have been measured. When no noble metal is included, the films exhibit strong antiparallel coupling between adjacent Fe layers, with saturation fields as large as 7 kOe, and giant magnetoresistance (GMR) of 6% at 300 K, similar to that of MBE (molecular beam epitaxy)-grown films reported by others. The interruption of intimate contact between Fe and Cr at the interface resulting from noble-metal deposition gives rise to a substantial decrease in the magnitude of the GMR and the interfacial coupling. This suggests that the mechanism of GMR is associated with Fe and Cr in contact, as is required by models invoking spin-dependent impurity scattering. The results also suggest that the antiparallel coupling arises from direct exchange. >

Anomalous X-ray scattering study of composition profile in Fe/Mn superlattice films

The wavelength dependence of the X-ray diffraction peak intensity in the small-angle region has been measured on two Fe/Mn superlattice films using synchrotron radiation. Peak intensities are found to be greatly enhanced at a wavelength slightly longer than the K-absorption edge of the Mn atom (1.896 AA), where the contrast in X-ray scattering power of the adjacent Fe and Mn layers becomes significantly large because of the effect of anomalous dispersion. Higher-order reflections up to the seventh are observed for (Fe(15 AA)/Mn(50 AA))40 and up to the third for (Fe(20 AA)/Mn(20 AA))100. Analysis of the peak width and intensity reveals intermixing of the atoms extending over several atom layers ( approximately 10-12 AA) at Fe/Mn interfaces and the fluctuation of the superlattice period within approximately 3-4 AA.

The Magnetic Structure of Fe2As

The magnetic structure of Fe 2 As has been determined by neutron diffraction. The compound Fe 2 As is antiferromagnetic with the Néel point at about 80°C. Its magnetic structure is different from Mn 2 As. The coupling between layers of iron atoms Fe(II) located at (0, 1/2, z ) and (1/2, 0, \bar z ) is antiparallel, but the coupling between a layer of iron atoms Fe(I) located at (0, 0, 0), (1/2, 1/2, 0) and adjacent Fe(II) layers is parallel. The magnetic unit cell has the c -axis twice as large as that of the chemical unit cell. The magnetic moments are 1.28 and 2.05 Bohr magnetons for Fe(I) and Fe(II) atoms. respectively. The moments lie perpendicular to the c -axis.