Direct measurement of spin-dependent conduction-electron mean free paths in ferromagnetic metals

Gurney, B. A.; Speriosu, V. S.; Nozières, J. P.; Lefakis, H.; Wilhoit, Dennis R.; Need, Omar U.

doi:10.1103/physrevlett.71.4023

Cited by 199 publications

(73 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…He observed that the proportionality constant between long and the conductivity in nonmagnetic alloys like Cu 80 Au 20 and Cu 10 Au 90 is essentially the same as that found in the structures with ferromagnetic Co and alloys such as Ni 81 Fe 19 and Ni 12 Co 88 , which leads to the conclusion that for all of these materials short Ϸ long , although this refers to room temperature only. The absence of a considerable bulk spin-dependent scattering is in striking contrast with Gurney et al 14 who reported a Co ↓ р6 Å from analysis of ⌬G as a function of d Co in backed spin-valves of the basic composition Co͑d Co Å͒/NiFe͑20 Å͒/ Cu͑23 Å͒/NiFe͑50 Å͒/FeMn͑80 Å͒. However, meaningful and quantitative comparison with these results is difficult, because in their analysis the impact of averaging over all electron angles was not recognized, which leads to a too crude simplification ⌬Gϰ1Ϫexp͑Ϫt/ long ͒.…”

Section: Discussioncontrasting

confidence: 53%

“…8 the longest of the Co mean free paths is estimated via Co ↑ ϭ2 ͑open circles͒ and is shown to decrease with increasing temperature, in agreement with a lower conductivity due to increasing phonon scattering at higher temperatures. The figure is supplemented with data obtained by Parkin, 13 Dieny and co-workers, 2,8 and Gurney et al 14 who have determined in a similar way a characteristic length from magnetoresistance measurements on related structures. We think that the observed discrepancies are a consequence of the growth conditions of the samples, which may have obviously a considerable impact on scattering lengths.…”

Section: Discussionmentioning

confidence: 88%

“…3 we present room temperature measurements of G, ⌬G, and GMR ratio for the third series of spin-valves, composed of Co/Cu/Co/Cu, as a function of the position t of the shifting 5 Å Ru barrier through Cu. We will refer to the top Co layer as the filter layer and to the Cu layer as the back layer, a concept originally introduced by Gurney et al 14 First, the sheet conductivity shows similar behavior as for the Co/Cu/Co spin-valves, with a minimum in the conductivity for intermediate values of t. Next, ⌬G increases as a function of t, and although ⌬G does not saturate completely we can identify an exponential behavior demonstrated by the exponential fit of ⌬G ͑solid line͒. For tϭ0 Å it is observed that the differential conductivity ⌬G has an offset, which we attribute to the Co/Cu/Co part of the sample.…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Analysis of scattering lengths in Co/Cu/Co and Co/Cu/Co/Cu spin-valves using a Ru barrier

et al. 1996

View full text Add to dashboard Cite

We use uncoupled Co/Cu/Co and Co/Cu/Co/Cu spin-valve structures with a Ru barrier shifted through the top Co and Cu layer, respectively, to measure the longest of the electron mean free paths in Co and Cu as originally suggested by Parkin. From semiclassical transport calculations and careful analysis of the magnetoresistance data we conclude that the exponential behavior of ⌬G is uniquely related to the longest of the Co and Cu mean free paths under the condition of effective spin-dependent filtering at the interfaces or in the bulk of the Co. In this regime we have compared long in Co and Cu with bulk conductivities ͑ϰ short ϩ long ͒, yielding no strong evidence for bulk spin-dependent scattering in Co. ͓S0163-1829͑96͒02037-1͔

show abstract

Section: Discussioncontrasting

confidence: 53%

Section: Discussionmentioning

confidence: 88%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Analysis of scattering lengths in Co/Cu/Co and Co/Cu/Co/Cu spin-valves using a Ru barrier

et al. 1996

View full text Add to dashboard Cite

show abstract

“…However, it is interesting to note that the mean free paths in Ref. 6 are close to the majority electron mean free path in this work. The mean free path in sputtered polycrystalline samples is strongly affected by structural defects and impurities.…”

mentioning

confidence: 60%

The role of interfaces in the magnetoresistance of Au/Fe/Au/Fe/GaAs(001)

Enders

Monchesky

Myrtle

et al. 2001

Journal of Applied Physics

View full text Add to dashboard Cite

The electron transport and magnetoresistance (MR) were investigated in high quality crystalline epitaxial Fe(001) and Au(001) films and exchange coupled Au/Fe/Au/Fe/GaAs(001) trilayer structures. Fits to the experimental data were based on the semiclassical Boltzmann equation, which incorporates the electronic properties obtained from first-principles local density functional calculations. The fits require a surprisingly high asymmetry for the spin dependent electron lifetimes in Fe, τ↓/τ↑=10 at room temperature. Despite the large atomic terraces at the Au/vacuum and Fe/GaAs interfaces the scattering at the outer interfaces was found to be diffuse. The origin of MR in Au/Fe/Au/Fe/GaAs(001) structures is due to electron channeling in the Au spacer layer. The measured MR is consistent with the diffusivity parameters s↑=0.55, s↓=0.77 at the metal–metal interfaces.

show abstract

“…φ , where v F = 0.2 × 10 6 m/s is the Fermi velocity in Py [22], l ↓ e ∼ 0.6 nm is the elastic mean free path for minority electrons [22,23], and L φ is the dephasing length. Assuming that the voltage correlation scale V c ∼ max{k B T /e, E c /e}, we find a rough lower limit on the dephasing length, L φ 16 nm.…”

mentioning

confidence: 99%

Anisotropic Magnetoresistance and Anisotropic Tunneling Magnetoresistance due to Quantum Interference in Ferromagnetic Metal Break Junctions

2006

View full text Add to dashboard Cite

We measure the low-temperature resistance of permalloy break junctions as a function of contact size and the magnetic field angle, in applied fields large enough to saturate the magnetization. For both nanometer-scale metallic contacts and tunneling devices we observe large changes in resistance with angle, as large as 25% in the tunneling regime. The pattern of magnetoresistance is sensitive to changes in bias on a scale of a few mV. We interpret the effect as a consequence of conductance fluctuations due to quantum interference. PACS numbers: 72.25.Ba; 73.63.Rt; 75.75.+a The magnetoresistance properties of nanometer-scale magnetic devices can be quite different from those of larger samples. One aspect of this difference has been explored extensively in previous experiments -the resistance of magnetic domain walls created when the magnetic moment direction in one magnetic electrode is rotated relative to the moment in a second electrode [1,2,3,4,5,6,7,8,9]. Here we focus on a different aspect of the physics of magnetoresistance in nanoscale magnetic contacts -the anisotropic magnetoresistance (AMR) that arises when the magnetization throughout a device is rotated uniformly so as to change the angle between the direction of current flow and the magnetic moment. Our measurements are motivated by predictions of increased AMR for atomic-sized ballistic conductors [10] and indications of enhanced AMR in Ni contacts [8]. By making detailed studies of resistance as a function of field angle using mechanically-stable permalloy contacts, we show that the size of the AMR signal at low temperature can increase dramatically as the contact cross section is narrowed to the nanometer-scale regime. Even more strikingly, we find that point contacts which are completely broken, so as to enter the tunneling regime, also exhibit a tunneling anisotropic magnetoresistance effect (TAMR) as large as 25% when the magnetic-moment directions in the two contacts are rotated together while remaining parallel.Magnetostriction and magnetostatic forces can alter the geometry of nanoscale junctions as the magnetic field is varied, and produce artifacts in the resistance, so experiments must be designed to minimize these effects [5,6,7]. For this reason, our contacts are firmly attached to a non-magnetic silicon substrate and are measured entirely at low temperature to suppress thermally-driven surface diffusion of metal atoms. Similar structures have proven [8,9] to be much more mechanically-stable than previous samples which were measured at room temperature. We fabricate our devices using aligned steps of electron beam lithography to first pattern 20-nm-thick gold contact pads and then 30-nm-thick magnetic permalloy (Py = Ni 80 Fe 20 ) point contacts [9]. Each contact con- sists of two elongated electrodes which are connected by a 100-nm-wide bridge ( Fig. 1(b)). The magnetic field B is applied using a 3-coil vector magnet capable of 0.9 T in any direction and up to 7 T along one axis (the x axis, defined below) with the other two coils t...

show abstract

Direct measurement of spin-dependent conduction-electron mean free paths in ferromagnetic metals

Cited by 199 publications

References 28 publications

Analysis of scattering lengths in Co/Cu/Co and Co/Cu/Co/Cu spin-valves using a Ru barrier

Analysis of scattering lengths in Co/Cu/Co and Co/Cu/Co/Cu spin-valves using a Ru barrier

The role of interfaces in the magnetoresistance of Au/Fe/Au/Fe/GaAs(001)

Anisotropic Magnetoresistance and Anisotropic Tunneling Magnetoresistance due to Quantum Interference in Ferromagnetic Metal Break Junctions

Contact Info

Product

Resources

About