Microscopic mechanisms of giant magnetoresistance

Vouille, C.; Barthélémy, A.; Mpondo, F. Elokan; Fert, A.; Schroeder, P. A.; Hsu, Shih-Ying; Reilly, A. C.; Loloee, R.

doi:10.1103/physrevb.60.6710

Cited by 100 publications

(95 citation statements)

References 40 publications

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“…The inverse GMR was also found in other multilayers of the type FM/Cu/Co/Cu, where FM=Ni 1-x Cr x , Co 1-x Cr x , Co 1-x Fe x and Fe 1-x V x . 81,82 The comparison of the bulk scattering spin asymmetries α FM extracted from these experiments with the previous results obtained for bulk alloys 31,32 shows that the sign of α FM is the same but the magnitude is generally much smaller. The inversion of GMR in the experiments of Hsu et al 82 and Vouille et al 81 appears to occur at thicknesses of the FM layer above a certain critical thickness, so that there was a crossover in the sign of GMR at this thickness.…”

Section: Impurity Dependencementioning

confidence: 84%

“…81,82 The comparison of the bulk scattering spin asymmetries α FM extracted from these experiments with the previous results obtained for bulk alloys 31,32 shows that the sign of α FM is the same but the magnitude is generally much smaller. The inversion of GMR in the experiments of Hsu et al 82 and Vouille et al 81 appears to occur at thicknesses of the FM layer above a certain critical thickness, so that there was a crossover in the sign of GMR at this thickness. This was ascribed to the competition between bulk scattering in the FM, which has spin asymmetry α bulk <1, and interface scattering at the FM/Cu interface, which was assumed to have spin asymmetry α int >1.…”

Section: Impurity Dependencementioning

confidence: 84%

“…acquires an opposite sign) if the spin asymmetries in scattering are opposite in consecutive ferromagnetic layers. Vouille et al 81 have found that Ni 95 Cr 5 /Cu/Co/Cu multilayers, in which Ni layers are doped by 5% of Cr impurities, display the inverse GMR when Ni 95 Cr 5 thickness is more than 2nm. According to Campbell and Fert 32 Cr impurities in Ni scatter more strongly the majorityspin electrons, which makes the bulk scattering spin asymmetry of the NiCr layers less than unity, i.e.…”

Section: Impurity Dependencementioning

confidence: 99%

See 2 more Smart Citations

Perspectives of giant magnetoresistance

Tsymbal¹,

Pettifor²

2001

Solid State Physics

252

189

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Section: Impurity Dependencementioning

confidence: 84%

Section: Impurity Dependencementioning

confidence: 84%

Section: Impurity Dependencementioning

confidence: 99%

See 1 more Smart Citation

Perspectives of giant magnetoresistance

Tsymbal¹,

Pettifor²

2001

Solid State Physics

252

189

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“…Together, theory and experiment [26][27][28][29][30] indicate that both a dilute Fe(Cr) alloy and an Fe(Cr)/Cr interface should scatter majority electrons more strongly. In this paper we show that an Fe(Cr)/Cr/Fe(Cr) trilayer displays the two behaviors described in the previous paragraph, namely a normal MR-resistance smallest in the high field P-state, but an inverted current-driven switching-positive current drives the system to the lower resistance P state and negative to the higher resistance AP state Magnetic nanopillars of approximately elliptical shape and dimensions ~ 70 nm x 130 nm were prepared by triode sputtering onto Si substrates.…”

mentioning

confidence: 99%

Inverted current-driven switching in Fe(Cr)/Cr/Fe(Cr) nanopillars

AlHajDarwish

Fert

Pratt

et al. 2004

Journal of Applied Physics

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From both theory and experiment, scattering of minority electrons is expected to be weaker than scattering of majority electrons in both dilute Fe(Cr) alloys and at Fe(Cr)/Cr interfaces. We show that Fe(Cr)/Cr/Fe(Cr) trilayer nanopillars display a normal magnetoresistance--i.e., largest resistance at low magnetic fields and smallest at high fields, but an inverted current-driven switching--i.e., positive current flowing from the fixed to the reversing layer switches the trilayer from higher to lower resistance, and negative current switches it from lower to higher.Comment: 3 pages, 3 figs., accepted for J. Magn. Magn. Mat., MMM/Intermag Conf. 200

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“…The coupling is found to be much stronger than that between continuous ferromagnetic layers. PACS: 75.70.Ak, 75.47.De, 75.75.+a GMR (giant magnetoresistance) and TMR (tunneling magnetoresistance) devices are primary candidates in future magneto-electronic applications and media [1,2,3,4,5]. The ability to create arrays of magnetic junctions on micro sized areas can enhance storage size drastically and enable the production of non volatile ultra-dense RAM chips.…”

mentioning

confidence: 99%

Zero field resistance dip in magnetic tunnel junctions employing a granular electrode

Barness

Frydman

2005

Phys. Rev. B

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We present magnetoresistance (MR) measurements performed on magnetic tunnel junctions in which one of the electrodes is a granular ferromagnetic film. These junctions exhibit a zero field resistance dip. The dip magnitude depends on the size of the grains. We interpret these results as a consequence of the orange peel effect between the continuous ferromagnetic film and the magnetic grains. The coupling is found to be much stronger than that between continuous ferromagnetic layers. PACS: 75.70.Ak, 75.47.De, 75.75.+a GMR (giant magnetoresistance) and TMR (tunneling magnetoresistance) devices are primary candidates in future magneto-electronic applications and media [1,2,3,4,5]. The ability to create arrays of magnetic junctions on micro sized areas can enhance storage size drastically and enable the production of non volatile ultra-dense RAM chips. Granular ferromagnets have a promising potential to act as a further step in this direction since a single junction may be able support numerous bits, considerably increasing the possible storage densities.All applications based on GMR and TMR effects require high quality multilayers constructed of thin ferromagnetic and non-magnetic films. The performance of the devices depend strongly on the morphological and structural properties of the films as well as their physical characteristics. Among the crucial factors is the interlayer coupling between two ferromagnetic layers separated by a non-magnetic spacer. This coupling may be a sum of several different mechanisms, of which three appear to be dominant. The first is pinhole coupling, which results from structural defects in the spacer and may destroy MR effects altogether. The second is the RKKY interaction which oscillates with the spacer thickness. This coupling is due to indirect exchange mechanism and applies only to conductive barriers (GMR multilayers). The third mechanism is the Néel Coupling [6], also named Orange Peel Effect (OPE), which applies both to conducting and to insulating spacers. This coupling utilizes the surface waviness of correlated layers to produce ferromagnetic interaction between ferromagnetic layers that could otherwise be antiferromagnetically coupled. The mechanism is based on the fact that the waviness of the magnetic film creates dipoles on the surface. A second layer with correlated waviness placed on top and separated by a non-magnetic spacer, experiences similar moment orientation due to dipole-dipole interaction as illustrated in figure 1a. Such ferromagnetic coupling reduces the GMR signal which requires antiferromagnetic orientation at low fields. Hence, a lot of effort is invested in an attempt to minimize this coupling in order to improve the performance of GMR/TMR elements [7,8,9,10,11,12]. The basic Néel model was derived for two infinitely thick magnetic layers separated by a non magnetic spacer [6]. Kools et al [13] extended the theory to included the finite size of the magnetic layers and obtained the following expression for the coupling strength:where h and λ are the a...

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Microscopic mechanisms of giant magnetoresistance

Cited by 100 publications

References 40 publications

Perspectives of giant magnetoresistance

Perspectives of giant magnetoresistance

Inverted current-driven switching in Fe(Cr)/Cr/Fe(Cr) nanopillars

Zero field resistance dip in magnetic tunnel junctions employing a granular electrode

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