Giant magnetoresistance in sputtered (Co70Fe30)xAg1-xheterogeneous alloys

Teixeira, Sérgio R.; Diény, B.; Chamberod, A.; Cowache, C.; Auffret, S.; Auric, P.; Rouvière, J. L.; Redon, O.; Pierre, J.

doi:10.1088/0953-8984/6/28/026

Cited by 19 publications

(7 citation statements)

References 18 publications

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“…Even for this concentration, the FC curve does not become completely flat, as has been observed for similar concentrations in Co-SiO 2 granular films 15 and in metallic CoFe-Ag alloys. 31,32 This feature seems to indicate the absence of strong magnetic interactions between particles for Co concentrations up to about x = 0.30, as may also be deduced from the relatively small values of . Sankar et al 33 reported = −29 K and = −34 K for Co-SiO 2 granular films with x = 0.32 and x = 0.41, respectively.…”

Section: A DC Susceptibilitymentioning

confidence: 51%

Tunneling magnetoresistance inCo−ZrO2granular thin films

et al. 2006

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Granular films composed of well defined nanometric Co particles embedded in an insulating ZrO 2 matrix were prepared by pulsed laser depositon in a wide range of Co volume concentrations ͑0.15Ͻ x Ͻ 0.43͒. High-resolution transmission electron microscopy ͑TEM͒ showed very sharp interfaces between the crystalline particles and the amorphous matrix. Narrow particle size distributions were determined from TEM and by fitting the low-field magnetic susceptibility and isothermal magnetization in the paramagnetic regime to a distribution of Langevin functions. The magnetic particle size varies little for Co volume concentrations x Ͻ 0.32 and increases as the percolation limit is approached. The tunneling magnetoresistance ͑TMR͒ was successfully reproduced using the Inoue-Maekawa model. The maximum value of TMR was temperatureindependent within 50-300 K, and largely increased at low T, suggesting the occurrence of higher-order tunneling processes. Consequently, the tunneling conductance and TMR in clean granular metals are dominated by the Coulomb gap and the inherent particle size distribution.

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Section: A DC Susceptibilitymentioning

confidence: 51%

Tunneling magnetoresistance inCo−ZrO2granular thin films

et al. 2006

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“…Below x v ϳ0.20, annealed samples display the typical features of a granular solid constituted by a random distribution of nanometric CoFe particles within the Cu matrix. 5,12,13 The maximum magnetoresistance observed in this family is about 20% at low temperature (Tϭ20 K and Hϭ10 kOe) for an x v ϭ0.16 sample annealed at 600°C. The change in magnetoresistance is defined as,…”

Section: Transport Propertiesmentioning

confidence: 83%

“…Fe was added to Co ͑about 5-10 at.%͒ in the classical CoCu GMR system as a minor FM component, in order to increase the GMR effect as previously reported, 5 by increasing the magnetic moment of the particles. Although the physical microstructure is almost the same for all the as-cast samples below the percolation threshold, magnetic and magnetotransport properties change dramatically with x v .…”

Section: Introductionmentioning

confidence: 99%

CoFe–Cu granular alloys: From noninteracting particles to magnetic percolation

Franco

Batlle

Labarta

1999

Journal of Applied Physics

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CoFe-Cu granular films with ferromagnetic content ranging from 0.10 to 0.33 by volume were prepared by radio frequency sputtering. As-cast samples were rapidly annealed at various temperatures up to 750°C to promote the segregation of CoFe particles within the metallic matrix. Magnetic and transport properties suggested that this family of samples may be classified into three groups: ͑i͒ below about 0.20 volume content of CoFe, all samples display the typical features of a granular solid constituted by a random distribution of nanometric CoFe particles within a Cu matrix, and the maximum magnetoresistance is about 20% at low temperature ͑giant magnetoresistance͒; ͑ii͒ for as-cast samples within 0.20 and 0.30 of volume concentration, magnetoresistance and magnetization display complex bimodal behavior and large metastable effects associated with the interparticle interactions, which stabilize a domain-like microstructure well below the volume percolation threshold ͑0.55͒, as already observed in CoFe-Ag͑Cu͒ granular alloys. As a consequence of the large magnetic correlations, magnetoresistance is very low ͑1%-3%͒. Through annealing, the microstructure and therefore the transport properties evolve to those of a classical giant magnetoresistance system with large particles; and ͑iii͒ above about 0.30 of volume content ͑and still below the volume percolation threshold͒, as-cast samples display both anisotropic and giant magnetoresistance, as also observed in other granular alloys. Annealing leads to complete segregation and to the formation of large magnetic particles, which results in a transition from mixed behavior of both anisotropic and giant magnetoresistance ͑GMR͒ regimes to a giant magnetoresistance regime, with a maximum GMR of about 7%.

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“…10,11 In particular, systems with Fe 30 Co 70 / Cu alloy compositions exhibited one of the largest magnetoresistance amplitude reported so far at 4 K in granular alloys. 12,13 Nowadays, Fe x Co 1−x systems are also used in magnetic tunnel junctions with spin-valve architecture such as magnetic tunnel transistor devices. 14 In order to understand the magnetic behavior of the Fe 30 Co 70 / Cu multilayers under ion irradiation it is necessary first to investigate the structural evolution.…”

Section: Introductionmentioning

confidence: 99%

Structural modifications in FexCo1−x∕Cu multilayers induced by ion irradiation

Graff

Teixeira

Amaral

et al. 2004

Journal of Applied Physics

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The structural evolution of Fe 30 Co 70 / Cu multilayers under ion irradiation is investigated in detail using x-ray techniques. The samples were irradiated with two different ions, 50 keV of He + and 600 keV of Kr + , at room temperature. No substantial changes were observed after He + irradiation; the He + ions promote some disorder in the FeCo layers, an increase of the Cu͑111͒ texture, and grain size. After Kr + irradiation a structural phase transition from bcc to fcc occurs in the FeCo layers. A very pronounced increase of the Cu͑111͒ texture and grain size is also observed. According to the equilibrium phase diagrams such fcc phase is not expected for the FeCo alloy at the composition of Fe 30 Co 70 . This fcc phase is imposed by the Cu fcc structure of the adjacent layers, which induce the regrowth of the FeCo layers structure from bcc to fcc during the relaxation period of the atomic collision cascades. Also, after the Kr + irradiation a multilayer structure still persists, as showed by the x-ray reflectivity.

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Giant magnetoresistance in sputtered (Co₇₀Fe₃₀)_xAg_1-xheterogeneous alloys

Cited by 19 publications

References 18 publications

Tunneling magnetoresistance inCo−ZrO2granular thin films

Tunneling magnetoresistance inCo−ZrO2granular thin films

CoFe–Cu granular alloys: From noninteracting particles to magnetic percolation

Structural modifications in FexCo1−x∕Cu multilayers induced by ion irradiation

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