Exchange coupling of ferromagnetic films across nonmagnetic interlayers
15 Apr 1987-Journal of Applied Physics (American Institute of Physics)-Vol. 61, Iss: 8, pp 3753-3755
TL;DR: In this article, exchange coupling between ferromagnetic films across nonmagnetic intermediate layers by means of light scattering from spin waves and microwave absorption was studied and it was shown that the effective interlayer exchange decreases when the interlayer thickness d0 increases.
Abstract: We have studied exchange coupling between ferromagnetic films across nonmagnetic intermediate layers by means of light scattering from spin waves and microwave absorption. The ferromagnetic films were Ni0.8Fe0.2 (permalloy) and Fe and we chose Au, Ag, Cu, V, Cr, Pd, Ge, Si, Mn, and Bi as nonmagnetic interlayer materials. As expected the effective interlayer exchange decreases when the interlayer thickness d0 increases. Minimum thickness d0 where the ferromagnetic films are exchange decoupled range between 10 and 40 A. We compare these results with the concentration dependence of the magnetic ordering temperature in alloys of Fe and Ni with other elements, taking this as a measure for the strength of the exchange. There is a good correspondence which indicates that the coupling effects in the layered structures and the alloys have the same origin which is presumably by RKKY interaction.
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TL;DR: In this article, the magnetic and magnetotransport properties of several series of sandwiches consisting of two ferromagnetic layers (Ni, Co, Ni80Fe20) separated by a noble metal (Cu, Ag, Au) are described.
Abstract: The magnetic and magnetotransport properties of several series of sandwiches consisting of two ferromagnetic layers (Ni, Co, Ni80Fe20) separated by a noble metal (Cu, Ag, Au) are described. In order to vary the relative orientation of the magnetizations of the two ferromagnets, one of them was constrained by exchange anisotropy (e.g., NiFe/Fe50Mn50). The ferromagnetic layers are magnetically soft and not coupled antiparallel, giving very large changes of resistance at low fields. At room temperature relative changes ΔR/R of 4.1% in 10 Oe for Si/Ta 50 A/NiFe 62 A/Cu 22 A/NiFe 40 A/FeMn 70 A/Ta 50 A and 8.7% in 20 Oe has been obtained for a structure based on Co/Cu/Co layers. The magnetoresistance versus the thickness of the ferromagnetic layer shows a broad peak near 80 A for Ni, Co and NiFe, demonstrating the importance of bulk rather than interfacial spin‐dependent scattering, in contrast to Fe/Cr multilayers. The magnetoresistance decreases exponentially with increasing interlayer (Cu and Au) thickness,...
531 citations
TL;DR: In this article, the spin wave spectra of exchange-coupled epitaxial double-layers of bcc ferromagnetic material with the (100) and (110) surfaces were analyzed theoretically within the classical continuum model.
52 citations
TL;DR: In this article, the authors used ferromagnetic resonance (FMR) at 33 GHz to study the properties of a number of evaporated thin Fe film systems and derived values for effective anisotropy field HKeff, g value, and exchange constant A were derived.
Abstract: We have used ferromagnetic resonance (FMR) at 33 GHz to study the properties of a number of evaporated thin Fe film systems. Values for effective anisotropy field HKeff , g value, and exchange constant A were derived. For Fe on glass, ‖HKeff ‖ was found to increase with increasing thickness. These changes were attributed to stress which decreased with film thickness. The presence of a Cu or a Ti underlayer did not seem to affect HKeff for films grown at room temperature. However, Fe/Ti/glass films made at higher substrate temperatures, Ts, did show an increase in ‖HKeff ‖. The appearance of a spin‐wave mode in the Fe films enables us to compute the exchange constant A for Fe, A=(2.12±0.14)×10−6 ergs cm−1. The coupling between two thin Fe films through an intervening Cu layer was investigated. A model predicting the number and position of the peaks in the spectrum as a function of coupling is presented. From experiment it was observed that the coupling remains almost constant through the 50–5‐nm Cu thickne...
41 citations
01 Jan 2000
40 citations
01 Jan 1989
TL;DR: In this paper, the spinwave modes occurring in layered magnetic structures are discussed and the coupled modes can be used to explore the interlayer exchange interaction, which can be either via oscillating dipolar fields caused by the preceding spins, or via the exchange interaction.
Abstract: The spinwave modes occurring in layered magnetic structures are discussed. Experimental examples obtained by means of light scattering are presented. Emphasis is put on coupled modes occurring in magnetic double layers, i.e. two ferromagnetic films, separated by a nonferromagnetic interlayer. The coupling can be via oscillating dipolar fields caused by the preccessing spins, or via the exchange interaction. It is shown, how the coupled modes can be used, to explore such interactions. These investigations have led to the discovery of the interlayer exchange interaction.
23 citations
References
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TL;DR: A microscopic magnetic antiphase domain structure has been observed in a single-crystal Gd-Y superlattice by neutron diffraction and oscillatory behavior is consistent with recent theoretical speculation that the Gd moments are coupled through the intervening Y via the Ruderman-Kittel-Kasuya-Yosida interaction.
Abstract: A microscopic magnetic antiphase domain structure has been observed in a single-crystal Gd-Y superlattice by neutron diffraction. Furthermore, this long-range antiferromagnetic correlation is found to occur in a multibilayer, in which each bilayer consists of ${N}_{\mathrm{Gd}}$ ferromagnetic atomic planes of Gd followed by ${N}_{\mathrm{Y}}$ planes of nonmagnetic Y, for ${N}_{\mathrm{Y}}={N}_{\mathrm{Gd}}=10$ but not for ${N}_{\mathrm{Y}}=6 or 20$. This oscillatory behavior is consistent with recent theoretical speculation that the Gd moments are coupled through the intervening Y via the Ruderman-Kittel-Kasuya-Yosida interaction.
257 citations
TL;DR: In this article, the authors present theoretical studies of basic magnetic response characteristics of superlattice structures formed from alternating layers of ferromagnetic and antiferromagnetic materials, each described through use of a localized spin model.
Abstract: We present theoretical studies of basic magnetic response characteristics of superlattice structures formed from alternating layers of ferromagnetic and antiferromagnetic materials, each described through use of a localized spin model. The geometry explored here is one in which the antiferromagnet consists of sheets parallel to each interface within which the spins are aligned ferromagnetically. The study of the classical (mean-field) ground state as a function of magnetic field shows that a sequence of spin-reorientation transitions occur, particularly for superlattices within which the antiferromagnetic constituent consists of an even number of layers. For the various phases, we present calculations of the spin-wave spectrum, and also the infrared absorption spectrum.
184 citations
TL;DR: In this article, the authors studied the spin-wave modes in magnetic multilayers and found that the amount of exchange can be tailored by choosing the proper materials or thickness for the nonmagnetic intermediate layers between the magnetic films.
Abstract: Spin‐wave modes in magnetic multilayers are of interest both for basic research and for application—for example, in microwave devices. Here I would like to discuss some ways to manipulate the mode spectra of such multilayers. One way, for example, would be to have reversed magnetization direction in adjacent layers which can be achieved by tailoring the coercive forces of the films in a proper way. The mode spectrum of such a system has been derived only recently and I would like to report a few important results. Also I would like to discuss the case where the films are coupled by exchange as well as by the dipolar interaction which is always there. Here the amount of exchange can be tailored by choosing the proper materials or thickness for the nonmagnetic intermediate layers between the magnetic films. We have studied these effects for a couple of Fe sandwiches with intermediate layers of various materials and find a short coupling length (<5 A) for V and Cr, and a long one (≲20 A) for Cu, Ag, Au, and ...
73 citations
TL;DR: In this article, Brillouin scattering from spin waves has been applied to thin ferromagnetic films and the Damon Eshbach (DE) surface wave has been observed at a mode crossing in Fe films under variation of the thickness.
Abstract: The new technique of Brillouin scattering from spin waves has been applied to thin ferromagnetic films Scattering from standing spin waves and the Damon Eshbach (DE) surface wave is observed The interaction of both types of waves at a mode crossing in Fe films under variation of the thickness d is investigated The results suggest the absence of surface anisotropy and pinning For d≲20 nm scattering from standing modes becomes too weak to be observed In contrast to this, for the DE mode there is a strong increase in the scattering intensity when the films have been evaporated onto the proper substrates It is shown that this is due to both an increase in the thermal DE mode amplitudes and multiple interference effects in the lightscattering process Very strong scattering is obtained from films with d≊5 nm There is also a remarkable Stokes‐Antistokes asymmetry, which persists down to d≲3 nm It comes from the elliptical spin‐precession characteristic for such small values of d and the strong metallic
43 citations
TL;DR: In this paper, the existence of a coupling between the magnetizations of two ferromagnetic films, separated by a thin layer of Au or of Cr, has been demonstrated by controlled oxidation, after evaporation of the intermediate layer.
Abstract: The existence of a coupling between the magnetizations of two ferromagnetic films, separated by a thin layer of Au or of Cr, has been demonstrated previously. We have studied the modification of this coupling by controlled oxidation, after evaporation of the intermediate layer. The interaction energy decreases in the same manner for both Cr and Au intermediate layers, independent of the evaporation temperature of these layers. The rate of decrease is a function of the temperature at which the first magnetic film is prepared. From these experiments we conclude that in both cases the coupling results from the existence of magnetic bridges between the magnetic layers, passing through gaps in the intermediate layer. A model for the behavior of the spins in such a bridge is presented and its consequences are compared with the experimental results.
33 citations