In extension of a recent study on submonolayer magnetism of Fe(110) on W(110) [1], we observed the interplay of morphology and magnetic order in Fe(110)-films prepared on W(110) at 300 K, in a range of coverages θ between the pseudomorphic monolayer (θ = 1) and the pseudomorphic double layer (θ = 2), using a combination of STM, SPLEED, CEMS and TOM. Whereas the Curie-temperatures of the monolayer and the double layer are given by Tc(ML) = 230K and Tc(DL) = 450K, respectively, we observe in an interval of 1.20< θ < 1.48 ML a gap of magnetic long range order, for temperatures down to 115K. In CEMS, we observe superparamagnetic fluctuations for T < Tc(ML), but magnetic short range order for T < Tc(ML). The surprising blocking of long range order in the gap can only be explained from a quasi-antiferromagnetic indirect coupling between double-layer islands.

We present first results of anisotropy and exchange coupling studies of a system with two different magnetic layers (Fe and Co) separated by a nonmagnetic Cr spacer. For the magnetic measurements we used the longitudinal magneto-optical Kerr effect and ferromagnetic resonance. The hysteresis data obtained from the trilayer were fit to a theoretical model which contains both bilinear and biquadratic coupling. The in-plane anisotropy was found to be four-fold with the same easy-axis orientation for both the Fe and the Co layers. An analysis of the easy-axishysteresis loops indicates long period oscillatory coupling and also suggests a short period coupling.

The interlayer exchange coupling has been studied in two trilayer structures:

(a) 5.7Fe/5Cu/1FecCu1-c/5Cu/10Fe(001), where c=0.0, 0.1, 0.2, 0.45 0.60

(b) 5.7Fe/5Cu/1CrcCu1-c/5Cu/10Fe(001), where c=0.1, 0.45, 0.8 and 1.0.

The intention of these studies was to identify the role of Fe and Cr atoms in the alloyed FecCu1-c and CrcCu1-c layers on the direct interlayer coupling which is facilitated by the Cu valence electrons. FMR, BLS and MOKE studies were used to determine the interlayer exchange coupling. Mossbauer spectroscopy was used to identify the magnetic state of the Fe atoms in the alloyed layer. The results showed that the presence of foreign atoms inside the Cu spacer significantly decreased the bilinear antiferromagnetic coupling between the Fe layers. In the low concentration limit the Fe and Cr atoms behaved in a similar manner. A significant difference was found in the high concentration limit where the Fe atoms start to be partially magnetically ordered.

The Anderson model of local-state conduction electron mixing is applied to the problem of interlayer magnetic coupling in metallic multilayered structures with palladium (Pd) spacer layers. An oscillation period of 5 spacer monolayers and the tendency towards ferromagnetic bias of the interlayer magnetic coupling that we obtain are consistent with the experimental data.

A number of studies have inferred the presence of an Fe-silicide in Fe/Si multilayers. Our transmission electron diffraction data provide direct evidence for the presence of an Fe-silicide. Despite similarities in structural coherence and saturation magnetization behavior for Fe/Si and Fe/{FeSi}, direct evidence for Fe-silicide only occurs for the Fe/{FeSi} multilayers.

We have observed time dependent magnetic switching in spin-valve sandwich structures of Cu/Co/Cu/Fe films grown on silicon and Kapton substrates and Permalloy/Co/Cu/Co films grown on NiO or NiO/CoO coated Si substrates. The giant magnetoresistance (MR) values ranged from 1 to 3 percent at room temperature. The films were grown by DC magnetron sputter deposition. Measurements were made on the time required for the MR to stabilize to about 1 part in 104 after the applied field was incremented. This time depends almost linearly on the amplitude of the timedependent MR change with a slope (time / ΔMR) of 20 000 to 30 000 s. Some samples took as long as 70 s to stabilize. The time dependent effects may be important for devices operating in these regions of the magnetoresistance curve. In addition, measurements were made on the time history of the MR value for a period of 75 s following a step change in the field from saturation. We observed that the time dependent behavior of the MR values of both experiments produced an excellent fit to a function of the form ΔMR(t) = α + β;ln(t) where ɑ and β are constants. This time dependence was consistent with the behavior of the magnetic aftereffect.

The ideal magnetic switching mechanism for many types of data storage, including hard disk recording, is isolated domain coherent rotation (Stoner-Wohlfarth switching). However, in typical Pd/Co multilayers with high coercivity, the dominant switching mechanism is domain wall motion, which causes noise in the read back signal. We show that the proper addition of elements, such as carbon, into Pd/Co multilayers reduces the coupling between adjacent magnetic domains. The reduction of magnetic coupling reduces the length scale over which incoherent switching occurs.

Recent reports of temperature dependent antiferromagnetic coupling in Fe/Si multilayers have motivated the generalization of models describing magnetic coupling in metal/metal multilayers to metal/insulator and metal/semiconductor layered systems. Interesting dependence of the magnetic properties on layer thickness and temperature are predicted. We report measurements that show the antiferromagnetic (AF) coupling observed in Fe/Si multilayers is strongly dependent on the crystalline coherence of the silicide interlayer. Electron diffraction images show the silicide interlayer has a CsCl structure. It is not clear at this time whether the interlayer is a poor metallic conductor or a semiconductor so the relevance of generalized coupling theories is unclear.

The occurrence of a weak in-plane uniaxial magnetic anisotropy in Fe thin films grown by molecular beam epitaxy onto (001)-oriented MgO substrates has been previously reported. We explain the occurrence of this anisotropy by measuring the in-plane tetragonal distortion of the cubic Fe lattice in a 800Å-thick film. The analysis of the full x-ray diffraction spectrum reveals a 0.1% difference between the two in-plane parameters. This small difference is sufficient to fully explain the observed anisotropy (≈20 Oe) using a standard magnetoelastic model. Although it is established that the uniaxial anisotropy results from the angle of incidence of the Fe atomic flux during deposition, the relationship between angle of incidence and in-plane tetragonalization is still unexplained. However, this anisotropy is shown to also occur in other epitaxial systems such as Ni80Fe20 on (111)Si. Control of this effect can help design epitaxial multilayer films with specific and reproducible magnetic states.

We have prepared epitaxial Fe(110)/Mo(110) multilayers by sputter deposition. These films exhibit a large uniaxial anisotropy and may be attractive as islanded in-plane recording media. The large uniaxial anisotropy is due to the intrinsic surface anisotropy of the Fe(110)/Mo(110) interface, which is of the same magnitude as the surface anistropy of the Fe(110)/W(110) interface but has a different sign (the surface anisotropy of the Fe(110)/Mo(110) interface prefers the [001] axis of magnetization). The magnetoelastic component of the anisotropy is not large. A novel magneto-optic technique was used to measure the transverse component of the magnetization and deduce information about the anisotropy and domain structure of the multilayers.

The magnetic anisotropy of epitaxial Gd(0001) films on W(110) is determined as a function of temperature (150 to 350 K) and film thickness (9 to 30 monolayers) by in situ ferromagnetic resonance. It is found that the usual analysis in terms of a thickness independent part KV and a thickness dependent contribution 2KS/d must be performed at the same reduced temperature t = T/Tc(d). Kv shows qualitatively the same temperature dependence as the magnetocrystalline anisotropy of bulk Gd. It changes in sign near 0.7 Tc and does not vanish at Tc. KS on the other hand decreases linearly from 1.2 meV/atom at 0.6.Tc to zero at Tc. It appears that the intrinsic origin for Kv and KS is fundamentally different. The vanishing of KS at Tc indicates that two-ion anisotropy (spin-spin interaction) is dominating the interface anisotropy. The non- zero KV(T≥Tc) is likely due to a single ion magnetic anisotropy which is known for bulk Gd.

We have used in situ polar Kerr effect measurements to study the magnetic anisotropy of X/Co/Y sandwich structures grown by MBE on Cu(111) buffers, where X and Y are variable thicknesses of Au. For fixed values of Y and in the case of an underlayer wedge, e.g. variable X value, we have found a sharp minimum in both coercive field and perpendicular anisotropy at ≈1 atomic layer of the Au underlayer. This anisotropy behavior is opposite to that of an Au overlayer deposited on a Co film, i.e. variable Y and fixed X.

Spin-reorientation transition in magnetic thin film sandwiched by nonmagnetic materials is clarified by means of the variational formalism. Phase diagrams of the magnetization configuration are presented. Scaling relations among the film thickness, exchange coupling and magnetic anisotropies are revealed. A formula for the interface anisotropy is presented.

The structure and properties of sputter NiFe thin film deposited on both thermal oxide and thin tantalum nitride have been studied. The magnetic anisotropy field HK increases to 8.2 Oe when the NiFe film was deposited on a thin tantalum nitride underlayer. Anisotropic stress was found on the sample film with tantalum nitride underlayer. Results of X-ray diffraction show that a thin tantalum nitride underlayer appears to promote a preferred crystalline orientation formation of the NiFe film. The induced magnetic anisotropy is attributed to the formation of the preferred crystalline orientation and the induced anisotropic magnetoelastic energy which is associated with the anisotropic stress of the sample film.

We have studied the structural origins of perpendicular magnetic anisotropy in amorphous Tb-Fe thin films by employing high energy x-ray scattering. The as-deposited films show a clear structural anisotropy, with a preference for Fe-Tb near-neighbors to align in the out-of-plane direction. Upon annealing, the magnetic anisotropy energy drops significantly, and we see a corresponding reduction in the structural anisotropy. The radial distribution functions indicate that the number of Fe-Tb near-neighbors increases in the in-plane direction, but does not change in the out-of-plane direction. Therefore, the distribution of Fe-Tb near-neighbors becomes more uniform upon annealing. We conclude that the observed reduction in perpendicular magnetic anisotropy energy is a result of this change in structure.

We report self-consistent band-structure calculations for the magnetism of Cr overlayers adsorbed on Fe(001) in order to study the role played by imperfect Fe-Cr interfaces, at the microscopic and macroscopic scales, on the total magnetisation. The surprisingly large reduction of the total magnetisation (≈ - 5 μB/interfacial atom) recently observed in Cr/Fe(001) through in situ magnetometer measurements is shown to be reproduced only when an interchange of one Cr and Fe monolayer at the interface after deposition of the second Cr monolayer occurs.

In this paper, we show that iron can be grown by MBE in a body centered tetragonal structure in (001) FeIr superlattices. The growth, structure and morphology of these superlattices are briefly resumed. A variation of the BCT Fe magnetic moment depending on the Jr thickness is observed. This variation is demonstrated to come from a variation of the BCT Fe atomic volume, due to the competition of the Fe and Ir stresses. A magnetic transition from a non-magnetic to a low spin ferromagnetic state depending on the atomic volume is thus observed.

We have studied the magnetic properties of very thin PdFe films grown by molecular beam epitaxy. The behavior expected for a 2D Heisenberg system - that is a variation of the susceptibility as exp(B/T) and a logarithmic dependence of the magnetization on the applied field - is observed in a certain range of temperature and field. This is in agreement with recent results of Webb et al [1].

A method based on the variation of the magnetization direction of each layer and Holstein- Primakoff transformation is presented to estimate the magnetization configuration in a superlattice of quantum ferromagnetic system with an interface between perpendicular and in-plane easy-axis layers. Numerical results on the magnetization configurations under different applied magnetic fields, critical field, and critical anisotropic parameter are given.

We have produced pseudomorphic FexMn1-x/Ir(100) superlattices having different stoichiometry (0.8 ≥ x ≥ 0.3). The alloy crystalline structure is body centered tetragonal with a c/a ratio between 1.18 and 1.26. Iron rich alloys are ferromagnetic when the corresponding bulk alloys are antiferromagnetic. Manganese rich alloys are certainly antiferromagnetic according to bulk magnetization measurements and Mössbauer effect results. The transition from a ferromagnet with a vanishing moment when x = 0.5 to an antiferromagnet is associated with a volume expansion.