Magnetic properties, interlayer exchange coupling and electric transport in Fe/Cr/Fe trilayers (original) (raw)
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Magnetic Exchange Coupling in Asymmetric Trilayers of Co/Cr/Fe
MRS Proceedings, 1995
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-axis hysteresis loops indicates long period oscillatory coupling and also suggests a short period coupling.
Interlayer exchange coupling and perpendicular electric transport in Fe/Si/Fe trilayers
Physical Review B, 2002
The interlayer exchange coupling and the perpendicular magnetoresistance of Fe/Si/Fe systems have been investigated within the fully relativistic screened Korringa-Kohn-Rostoker method and the Kubo-Greenwood equation considering interdiffusion effects, i.e., inhomogeneous Fe-Si alloy formation at the interfaces. It is shown that the experimentally observed strong antiferromagnetic interlayer exchange coupling is caused by the formation of Fe-Si alloys at the interface. Furthermore, our calculations give evidence that the small magnetoresistance, which has been observed experimentally in Fe/Si/Fe trilayers has a similar origin. The results presented here give no evidence for a direct connection between the magnetoresistance and interlayer exchange coupling in Fe/Si/Fe systems.
Ab initio study of CPP transport in Fe/Cr/Fe trilayers: influence of transition metal impurities
MRS Proceedings, 2002
The transport properties of Fe(001)/Cr/Fe(001) trilayers are discussed with respect to the influence of transition metal impurities in form of layers. We are able to show that the periodicity of the giant magnetoresistance is directly influenced by the interlayer exchange coupling (IEC). Furthermore, it is observed that the behavior of the IEC strongly depends on whether an impurity overlayer of Mn or V is used. It turns out that the size of the GMR is only little effected by 3d-transition metal impurities, which is in agreement with the experimental findings. The electronic and magnetic properties of the trilayers have been investigated within the fully relativistic, spin-polarized SKKR method and the LDA. The transport properties of the Fe/Cr/Fe systems have been derived from the fully relativistic spin-polarized Kubo-Greenwood equation.
Ab Initio Study of Electric Transport and Interlayer Exchange Coupling in Fe-Si-Fe Systems
Phase Transitions, 2003
We present a first principles study of the magnetoresistance (MR) perpendicular to the planes of atoms and the interlayer exchange coupling (IEC) in Fe/Si/Fe trilayers. In both cases the dependence on the number of spacer layers is investigated, whereby the spacer thickness ranges between 3 and 21Å for the IEC and extends to 33Å for the MR in order to obtain the asymptotic behavior. Additionally, the influence of alloy formation at the interfaces on the MR and the IEC is examined. The calculations of the electronic structure are performed * Corresponding author: Tel. +43 1 58801 15834; fax: +43 1 58801 15898, email: hh@cms.tuwien.ac.at within the fully relativistic spin-polarized screened Korringa-Kohn-Rostoker method and the transport properties are derived from the Kubo-Greenwood equation. Our results give evidence that interdiffusion is one of the origins of the small magnetoresistance, which is observed experimentally in Fe/Si/Fe trilayers. AFM coupling occurs for spacers thicker than 4Å which is in accordance with the experimental findings. It seems that interdiffusion stabilizes AFM coupling in Fe/Si/Fe trilayers.
Dependence of the interlayer exchange coupling on the constitution of the magnetic layers
Journal of Applied Physics, 1996
We describe the consequences on the interlayer exchange coupling by the addition of a small amount of Ag impurities within the Co layers of high crystalline quality Co/Cu/Co͑Ag͒ and Cu/ Ru/Co͑Ag͒ trilayers, while maintaining the integrity of the spacer layers. We discuss the consequent changes in the amplitude, period, and phase of the coupling in terms of the modification of interfacial spin-dependent potentials.
Journal of Physics: Condensed Matter, 2007
The ab initio full-potential linearized augmented plane-wave method explicitly designed for the slab geometry was employed to elucidate the physical origin of the layer potentials for the trilayers nFe/3Cr/nFe(001), where n is the number of Fe monolayers. The thickness of the transition-metal ferromagnet has been ranged from n = 1 up to n = 8 while the spacer thickness was fixed to 3 monolayers. The calculated potentials were inserted in the Fuchs-Sondheimer formalism in order to calculate the giant magnetoresistance (GMR) ratio. The predicted GMR ratio was compared with the experiment and the oscillatory behavior of the GMR as a function of the ferromagnetic layer thickness was discussed in the context of the layer potentials. The reported results confirm that the interface monolayers play a dominant role in the intrinsic GMR.
Magnetic exchange-coupling effects in asymmetric trilayer structures of MBE-grown Co/Cr/Fe
Physical Review B, 1996
We present results of anisotropy and exchange-coupling studies of asymmetric Co/Cr/Fe trilayers and superlattices grown by molecular beam epitaxy on Cr͑001͒/Mg͑001͒ buffers and substrates. The magnetic properties have been investigated using both the longitudinal magneto-optical Kerr effect and ferromagnetic resonance. The hysteresis data obtained from the trilayer system were fit to a theoretical model which contains both bilinear and biquadratic coupling. The effective in-plane anisotropy was found to be of fourfold symmetry with the same easy-axis orientation for both the Fe and Co layers. An analysis of the easy-axis hysteresis loops indicates long-period oscillatory coupling and also suggests a short periodic coupling. We show that weakly antiferromagnetically coupled asymmetric films might serve as potential candidates for improved spin-valve systems.
Interlayer exchange coupling in Co/Ru/Co trilayers
Journal of Magnetism and Magnetic Materials, 2005
The dependence of the interlayer exchange coupling in Si(0 0 1)/Ta/Co/Ru/Co/Ta trilayer on the thickness of the top Co layer is investigated. A strong in-plane uniaxial anisotropy is created in the magnetic layers by the shape anisotropy of an obliquely sputtered Ta underlayer, as confirmed by magnetometry and Brillouin light scattering measurements. The evolution of the magnetic properties, such as the magnetization at remanence and the saturation fields of the hysteresis loops and the giant magnetoresistance, is discussed in terms of the bilinear and biquadratic exchange coupling coefficients. r
Swift iodine ion modification of the structural and magnetotransport properties of Fe/Cr systems
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2009
Fe/Cr/Fe trilayers and (Fe/Cr) 20 multilayers prepared under ultrahigh vacuum conditions by thermal evaporation were irradiated with 200 MeV I 13+ ions in the fluence range between 1 Â 10 11 and 8 Â 10 12 I/cm 2 . The structural properties of the Fe/Cr/Fe trilayers and (Fe/Cr) 20 multilayers were measured by X-ray reflectivity (XRR) and conversion electron Mössbauer spectroscopy (CEMS). Magnetic exchange coupling between the Fe layers through the Cr spacer layer was observed by SQUID magnetization measurements. Magnetoresistance effect was measured using four probe method at room temperature. The XRR spectra showed an increase of the interface roughness versus increasing irradiation fluence in the multilayers, while in the trilayers smoothening of the interfaces in the sample irradiated with fluence equal to 4 Â 10 11 I/cm 2 and very slight change for other fluences were observed. Improving of the interface structure in the trilayers at this fluence was observed also by CEMS. Moreover the Mössbauer spectra also confirm roughening of the interfaces as a function of fluence for multilayers. Before irradiation an antiferromagnetic coupling fraction dominated in all samples. After irradiation the changes of magnetic coupling were different in both types of samples. The trilayers were less sensitive to the irradiation fluence than multilayers and an increase of the antiferromagnetic fraction at small fluences was observed. In the multilayers a continuous decrease of the antiferromagnetic fraction as a function of fluence was evidenced. Vanishing of the antiferromagnetic coupling, observed for the largest fluence, resulted in the decrease of magnetoresistance effect in the Fe/Cr multilayers.
Magnetic exchange coupling of Co/Ir multilayers
The European Physical Journal B, 2008
We present ab initio calculations of the exchange coupling for Co/Ir systems using a selfconsistent full-potential linearized augmented plane-wave (FLAPW) method. The local spin density approximation (LSDA) as well as the generalized gradient approximation of (GGA) are used to treat the exchange correlation potential. Structural optimization is considered for all systems due to the size difference between Co and Ir atoms. We obtain an oscillatory behavior for the interlayer exchange coupling with a period of 5.83Å, for both LSDA as well as GGA-PBE. The first antiferromagnetic peak is found for an Ir spacer of thickness 3.74Å, with strength of J = 51.09 mJ/m 2 for the GGA-PBE and 37.00 mJ/m 2 for the LSDA. PACS. 71.15.-m Methods of electronic structure calculations -73.61.-r Electrical properties of specific thin films