The current-in-plane resistivities and corresponding magnetoresistance ratios are calculated for realistic Co/Cu/Co-based spin-valve samples by applying the Kubo-Greenwood approach together with the fully relativistic, spin-polarized, screened Korringa-Kohn-Rostoker method for layered structures. We study the effects of both alloying in the spacer layers with a selection of 3d, 4d, and 5d elements as well as different profiles for interdiffusion at the Co/Cu interfaces. On comparing our results to available experimental data we find that both interdiffusion and confinement effects, due to the finite overall thickness of the spin valve, strongly influence the magnetoresistance of spin-valve structures.

Based on the fully relativistic spin-polarized screened Korringa-Kohn-Rostoker method and the Kubo-Greenwood eauation as formulated for layered systems the interlayer exchange coupling (IEC) as well as the magneto-resistance (MR) for the current in-plane (CIP) geometry is calculated for Fe/Cr/ Fe trilayer systems. For the IEC not only short periods of 2 monolayers (ML) but also long periods of about 18 ML are found. For large Cr thicknesses the magnetic moments oscillate with a period of 8-9 ML for even numbers of Cr layers and 18 for odd. The calculated CIP MR and corresponding resistivities are in the range of available experimental data. It is found that the peaks in the CIP MR have little in common with the oscillation periods characterizing the IEC.

Based on the Kubo-Greenwood equation as formulated for layered systems, an approach is discussed that allows us to separate the resistance of the current leads from that of the region whose resistance we wish to calculate for current perpendicular to the plane of the layers. By applying this approach to Fe/Ge/Fe model structures related to the parent lattice of bcc Fe we find that at least nine layers of the magnetic electrodes should be considered as being part of the calculation in order to perform such a separation. With different structures in the Ge spacer. we find that the concentration of vacancies plays a crucial role for the existence of a sizeable magnetoresistance (MR), while the actual structure in the spacer seems to be of less importance. Depending on the type of structure and the number of spacer layers (in a typical regime of 6-21 layers) the MR for ordered structure varies between 35% and 45%. Vacancy concentrations of more than 10%. however, wipe out the MR completely. Interdiffusion at the Fe/Ge interfaces produces very similar effects.

Within the Kubo-Greenwood formalism we use the fully relativistic, spin-polarized, screened Korringa-Kohn-Rostoker method together with the coherent-potential approximation for layered systems to calculate the resistivity for the permalloy series ${\mathrm{Ni}}_{c}{\mathrm{Fe}}_{1\ensuremath{-}c}.$ We are able to reproduce the variation of the resistivity across the entire series; notably the discontinuous behavior in the vicinity of the structural phase transition from bcc to fcc. The absolute values for the resistivity are within a factor of 2 of the experimental data. Also the giant magnetoresistance of a series of permalloy-based spin-valve structures is estimated; we are able to reproduce the trends observed on prototypical spin-valve structures.

Using the fully relativistic spin-polarized screened Korringa-Kohn-Rostoker method the magnetic properties of bulk NicFe1-c alloys, their free surfaces, and (free surfaces) of related spin valves of the type NicFe1-c/Co4Cu5Co4/NicFe1-c are calculated. It is found, that in the bulk systems the phase transition between fee and bce can be described very well in terms of spin and orbital magnetic moments, but also in terms of the magnetic anisotropy energy. The free surfaces and the spin-valve systems differ considerably from the corresponding bulk systems: free surfaces show a reorientation transition from a perpendicular orientation of the magnetization to in-plane at about 60% Ni, whereas the overall in-plane magnetization found in permalloy related spin valves can be mainly related to the contributions of the Co slabs to the band energy part of the magnetic anisotropy energy. In all cases investigated the (spin and orbital) magnetic moments for the free surfaces are considerably enhanced at the surface with similar effects pertaining at the interfaces and the surface of the spin valves.

The transmission matrix approach was used to evaluate the perpendicular magnetotransport in metallic multilayers on an abinitio level. The spin-polarized, surface Green function technique was employed within the framework of the tight-binding, linear muffin-tin orbital method. The effect of impurities was included in terms of lateral supercells with random arrangements of two types of atoms. This approach treats both the ballistic and the diffusive regimes of magnetotransport on equal footing. The method was also applied to face-centered-cubic-based Co/Cu/Co(001) trilayers.

The magnetic properties of (ConPdm)(r) superstructures on Pd(100) and Pd(111) are evaluated using the fully-relativistic spin-polarized screened Korringa-Kohn-Rostoker method. It is found that only in the case of a Pd(111) substrate such superstructures exhibit perpendicular magnetism, while on a Pd(100) substrate the magnetization is oriented in-plane. Also investigated is the effect of interdiffusion in repeated superstructures. By using the inhomogeneous coherent potential approximation (CPA) for layered systems the effect of ordering into (repeated) superstructures can be described in an ab-initio-like manner. It is found that already small amounts of interdiffusion can be decisive for the actual value of the magnetic anisotropy energy.

The transmission matrix approach is used to evaluate perpendicular magnetotransport in metallic multilayers that consist of two magnetic slabs separated by a non-magnetic spacer. We employ the spin-polarized surface Green function technique within the framework of the tight-binding linear muffin-tin orbital method. Our approach allows both the ballistic and the diffusive regime of magnetotransport to be treated on equal footing. The effect of disorder is included in terms of lateral supercells confined to individual atomic layers. In this paper, we apply the method to fcc-based Co/Cu/Co(001) trilayers.

The current-perpendicular-to-plane ~CPP! magnetotransport of a metallic sample sandwiched by two ideal leads is described at an ab initio level. The so-called ‘‘active’’ part of the system is either a trilayer consisting of two magnetic slabs of finite thickness separated by a nonmagnetic spacer or a multilayer formed by alternating magnetic and nonmagnetic layers. We use a transmission matrix formulation of the conductance based on surface Green’s functions as formulated by means of the tight-binding linear muffin-tin orbital method. The formalism is extended to the case of lateral supercells with random arrangements of atoms of two types, which in turn allows to deal with specular and diffusive scattering on equal footing, and which is applicable also to the case of noncollinear alignments of the magnetization in the layers. Applications refer to fcc-based Co/Cu/Co~001! trilayers and multilayers, considering in detail the effect of substitutional alloying in the spacer and in the magnetic layers, as well as interdiffusion at the interfaces.

The current-perpendicular-to-plane (CPP) magnetoconductance of a trilayer consisting of a spacer sandwiched between two ideal leads is described on an ab initio level. We employ the transmission matrix formulation of the conductance within the framework of the spin-polarized surface Green function technique as formulated in terms of the tight-binding linear muffin-tin orbital method. The formalism is extended to the case of lateral supercells in each layer with random arrangements of atoms which allows to treat both the ballistic and diffusive transports on equal footing. The application is made to fcc-based Co/Cu/Co(001) trilayers.

We have used the spin-polarized relativistic screened Korringa-Kohn-Rostoker method for layered systems together with the Kubo-Greenwood formalism and the coherent-potential approximation to describe electrical transport properties of magnetic multilayers. We are able to calculate resistivities and magnetoresistance of model structures with no adjustable parameters by simultaneously determining contributions to the giant magnetoresistance of multilayers coming from both the electronic structure and spin-dependent scattering off impurities. [S0163-1829(99)05125-5].

The magnetic properties of ConPt(100), Co-n/Pt(111), (Co0.5Pt0.5)(n)/Pt( 100), (CoPt)(n)/Pt(100), and (CoPt)(n)/Pt(111), n less than or equal to 15, are investigated using the relativistic spin-polarized screened Korringa-Kohn-Rostoker method. It is found that only the artiticial superstructures (CoPt)(n) /Pt(100) and (CoPt)(n) /Pt(111) show a perpendicular magnetic anisotropy beyond n = 10. For the free surfaces of Co on Pt in the case of the (100) orientation, a multiple reorientation transition below n =7 is found, while along (111) such a transition is predicted at about four layers of Co. For the homogeneous, statistically disordered alloy Co0.5Pt0.5 on Pt(100) the orientation of the magnetization remains in-plane for all n investigated. A comparison to experiment yields interesting insight into aspects of order and disorder, surface segregation, and phase separation frequently encountered in experimental studies of perpendicular magnetism in the Co/Pt system. [S0163-1829(99)00125-3].

: The functional dependence of the giant magnetoresistance (GMR) with respect to the relative angle between the orientations of the magnetization in the magnetic slabs of a trilayer system is calculated by using the Kubo-Greenwood formula for electrical transport together with the fully-relativistic spin-polarized screened Korringa-Kohn-Rostoker method for semi-infinite systems and the coherent potential approximation. It is found that the functional dependence of the GMR is essentially of the form .

The resistivity and giant magnetoresistance (GMR) of (Cu3Ni3) n embedded in Cu(100), for n ≤ 11, that originates from the electronic structure of these finite, yet otherwise perfect, systems is calculated for currents in the plane of the layers (CIP) by using the Kubo–Greenwood formula for semi-infinite systems and the fully relativistic, spin-polarized screened Korringa-Kohn-Rostoker method. We find that for this particular type of repeated structure the CIP resistivity decreases from about 6 to 2 cm as the number of repeats increases from 2 to 11, and the CIP-GMR while starting out at 4% for n = 2 goes up to 16% at n = 11.

The problem of superlattice symmetry, i.e., the question of periodicity along the growth direction (surface normal) in magnetic multilayer systems, is discussed using discrete Fourier transformations for the anisotropy energy, as well as, for the antiparallel and perpendicular interface exchange coupling. We analyze the system Cu(100)/(Cu3Ni3)(n), where n is the number of repetitions, for the case of free surfaces and surfaces capped semi-infinitely by Cu(100). It will be shown that for some magnetic properties, and only in certain situations, (almost) periodic behavior with respect to n applies, while for other properties an oscillatory behavior is characteristic. Also discussed are implications with respect to typical experimental situations and with respect to traditional supercell approaches.

Directional Compton profiles of the transition-metal alloys FeAl, CoAl, and NiAl have been measured. Both a conventional technique (resolution 0.55 a.u. of momentum), based on a 59.3-keV x-ray source with a solid-state detector, and a high-resolution spectrometer (0.15 a.u. of momentum) with 50-keV x rays from a synchrotron source have been used. The results are interpreted using a theory based on a full-potential linearized augmented-plane-wave method. The agreement between the experimental and the theoretical momentum density anisotropy is very good. It is shown that the anisotropies at low momenta are heavily influenced by the particular shape of the Fermi surface.

We found that formation of an ordered phase in alloyed magnetic layers induces new periods of exchange coupling oscillations in metallic multilayer systems. We studied on an ab initio level the case of c(2 X 2) ordering of random Co50Fe50(001) magnetic slabs embedded in fcc Cu. The origin of the new periods can be correlated to critical points of the spacer Fermi surface folded down to the Brillouin zone corresponding to the c(2 X 2) superlattice.