Antiferromagnetic exchange and magnetoresistance enhancement in Co-Re superlattices

Freitas, P. P.; Melo, L.V.; Trindade, Isabel; From, M.; Ferreira, J.M.; Monteiro, Pedro M. S.

doi:10.1103/physrevb.45.2495

Cited by 19 publications

(7 citation statements)

References 8 publications

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“…18 The large resistivity in our samples could be due to the relatively large resistivity of Re ͑18.6 vs 5.8 ⍀ cm for Co in bulk͒, 19 perhaps resulting from the high density of states at the Re Fermi energy, 20 in addition to interface and defect scattering. The magnetoresistance of hcp͑0001͒ oriented Co/Re multilayers has been found by other authors to be less than 2% at 18 K, 21 while our hcp (101 0) oriented superlattices have a MR larger than 3.5% at 5 K in certain geometries. In contrast to this previous Co/Re multilayer work, our samples are epitaxial, and therefore the AMR is more noticeable.…”

Section: Resultssupporting

confidence: 59%

Temperature dependence of the magnetoresistance in Co/Re superlattices onAl2O3
Charlton
¹
,
Lederman
²

2001
Phys. Rev. B

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Using a patterned hcp ͓Co ͑17 Å͒/Re (7Å)] 20 antiferromagnetically coupled superlattice, with the c axis in the film plane, magnetoresistance ͑MR͒ measurements were made in the temperature range between 5 K and room temperature. The MR was simulated and decomposed into its anisotropic magnetoresistance ͑AMR͒ and giant magnetoresistance ͑GMR͒ components using the magnetization as a function of angle determined from neutron reflectivity experiments. We find that the GMR is anisotropic and has a different temperature dependence than the AMR when IЌc and a similar dependence when Iʈc, where I is the applied current. This implies that interface spin-dependent scattering plays a more significant role when IЌc than when Iʈc.

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Section: Resultssupporting

confidence: 59%

Temperature dependence of the magnetoresistance in Co/Re superlattices onAl2O3
Charlton
¹
,
Lederman
²

2001
Phys. Rev. B

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“…For thin Re samples (t Re Ͻ1.0 nm), magnetoresistance measurements clearly indicate the presence of GMR, due to antiferromagnetic coupling between the Co layers, as was previously observed in ͑0001͒-oriented Co/Re multilayers. 5 In these samples the MR behavior is relatively complex due to the spin-flop transition which results in a competition between the GMR and AMR effects. Magnetization hysteresis loops also suggest that antiferromagnetic coupling may be present at other Re thicknesses, although further studies are necessary to unequivocally prove this.…”

Section: Discussionmentioning

confidence: 99%

“…3,4 A system that has not received as much attention is the Co/Re system. The largest GMR reported for Co/Re multilayers to date does not exceed 2% at 18 K. 5 In all of the past studies of Co/Re multilayers, the samples were hcp͓0001͔-oriented with no indication of in-plane epitaxy. 5,6 There is much interest in the interplay between strong uniaxial in-plane anisotropies and antiferromagnetic coupling between layers because the anisotropy can stabilize the domain structure in the material, significantly alter the GMR behavior, and provide knowledge about fundamental magnetic interactions.…”

Section: Introductionmentioning

confidence: 96%

“…The largest GMR reported for Co/Re multilayers to date does not exceed 2% at 18 K. 5 In all of the past studies of Co/Re multilayers, the samples were hcp͓0001͔-oriented with no indication of in-plane epitaxy. 5,6 There is much interest in the interplay between strong uniaxial in-plane anisotropies and antiferromagnetic coupling between layers because the anisotropy can stabilize the domain structure in the material, significantly alter the GMR behavior, and provide knowledge about fundamental magnetic interactions. The unusual magnetic and transport properties that this combination causes have been studied in Fe/ Cr͑211͒ superlattices, 7 Co/Cr multilayers, [8][9][10][11] and Co/Ir multilayers.…”

Section: Introductionmentioning

confidence: 96%

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Magnetic properties of Co/Rehcp(101¯0)superlattices

et al. 1999

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hcp(101 0) Co/Re superlattices were grown via magnetron sputtering on Al 2 O 3 (112 0) substrates. The thickness of the Co layers was approximately 1.8 nm with the Re layer thickness varying between 0.5 nm and 3.0 nm. Low angle x-ray reflectivity revealed that for our growth conditions the interfacial roughness is approximately 0.4 nm in each material at each interface. High angle x-ray diffraction, together with offspecular x-ray diffraction, showed that the growth is epitaxial with the ͓0001͔ axis in-plane and parallel to the Al 2 O 3 ͓0001͔ axis. Magnetization measurements indicate the presence of an in-plane uniaxial anisotropy in all samples and antiferromagnetic coupling when the Re layer thicknesses are less than 1.0 nm and close to 2.0 nm. The uniaxial anisotropy was measured via ferromagnetic resonance and determined to be approximately 5 times smaller than in bulk Co for thicker Re layer samples. For thin Re samples, a spin-flop transition causes a competition between the anisotropic magnetoresistance and the giant magnetoresistance when the external field is applied parallel to the easy axis. The most notable consequence is that the magnetoresistance is positive for small fields and negative for large fields when the current is perpendicular to the applied field. We also report a magnetoresistance of ϳ4.5% at 10 K, more than twice the maximum value previously reported for hcp͑0001͒ Co/Re multilayers. Co/Re hcp(101 0) superlattices provide a new system whereby the role of in-plane magnetic anisotropy in the magnetoresistance of metallic superlattices can be studied.

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“…Our analysis shows that the interesting dips in the MR are only due to AMR [15]. The magnetoresistance of hcp (0001) oriented Co/Re multilayers has been found by other authors to be less than 2 % at 18 K [18], while our superlattices have a MR larger than 3.5 % at 5 K in certain geometries. In contrast to this previous Co/Re multilayer work, our samples are epitaxial, and therefore the AMR is more noticeable.…”

Section: Pgxir (H)-p~ai -mentioning

confidence: 70%

Temperature Dependence of the Magnetoresistance of Co/Re Superlattices

2001

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Hcp (10.0) Co/Re superlattices were grown by dc magnetron sputtering on sapphire (11.0) substrates with the [00.1] direction of the superlattice in the film plane. The temperature-dependent magnetoresistance (MR) was measured on samples patterned by photolithography from 10 K to 300 K in a 5.5 T superconducting magnet. The pattern allows the measurement of the MR with the current (/) and the magnetic field (H) parallel or perpendicular to the magnetic easy axis (c, the [00.1] direction). Measurements at 5 K on an antiferromagnetically-coupled sample shows dips in the MR near H = 0 when H ]F c and H lI, dips below the saturation value at H -2.5 kOe for H II c and H I I configuration due to the competition between the anisotropic magnetoresistance (AMR) and the giant magnetoresistance (GMR). Since the AMR is dependent on the transport within the ferromagnetic layers, the temperature dependence yields information about the relative magnitudes of interface vs. bulk spin-dependent scattering. Our analysis shows that the GMR is anisotropic and that the spin-dependent scattering occurs predominantly at the interfaces only for certain configurations. INTRODUCTIONGiant magnetoresistance (GMR), discovered in the late 1980's [1], which occurs in magnetic multilayers and nanoparticles, and the anisotropic magnetoresistance (AMR), extensively studied since the 1930's in bulk ferromagnetic materials [2], are effects that have been recently under intense scrutiny due to their technological applications. Only relatively recently, however, have these two effects been studied in the same system. Some previously studied systems with both AMR and GMR include Co/Cr [3], Fe/Cr [4,5], Co/Ru [6], Co/Cu [7,8] and Permalloy/Cu [9] multilayers. These include experiments which separate the AMR and GMR in the same system [7] and experiments which focus on the enhancement of the GMR by AMR in systems with magnetocrystalline anisotropy, like Co/Cr multilayers [3].A topic of great current interest is determining the nature of the spin-dependent scattering responsible for GMR. Experiments where a monolayer or two of a magnetic material were added to the interface of a spin-valve [ 10] and the dependence of the GMR on interface roughness on Fe/Cr [4] show that in those systems the GMR depends strongly on scattering at the interfaces. But other studies show that the GMR depends on the film layer thickness [11], and that the GMR is dominated by bulk spin-dependent scattering [12].Here we summarize the results of a recent, comprehensive study of the temperature-

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Antiferromagnetic exchange and magnetoresistance enhancement in Co-Re superlattices

Cited by 19 publications

References 8 publications

Temperature dependence of the magnetoresistance in Co/Re superlattices onAl2O3
Charlton
¹
,
Lederman
²

2001
Phys. Rev. B

Temperature dependence of the magnetoresistance in Co/Re superlattices onAl2O3
Charlton
¹
,
Lederman
²

2001
Phys. Rev. B

Magnetic properties of Co/Rehcp(101¯0)superlattices

Temperature Dependence of the Magnetoresistance of Co/Re Superlattices

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Antiferromagnetic exchange and magnetoresistance enhancement in Co-Re superlattices

Cited by 19 publications

References 8 publications

Temperature dependence of the magnetoresistance in Co/Re superlattices onAl2O3Charlton1, Lederman2 2001Phys. Rev. B

Temperature dependence of the magnetoresistance in Co/Re superlattices onAl2O3Charlton1, Lederman2 2001Phys. Rev. B

Magnetic properties of Co/Rehcp(101¯0)superlattices

Temperature Dependence of the Magnetoresistance of Co/Re Superlattices

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Product

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Temperature dependence of the magnetoresistance in Co/Re superlattices onAl2O3
Charlton
¹
,
Lederman
²

2001
Phys. Rev. B

Temperature dependence of the magnetoresistance in Co/Re superlattices onAl2O3
Charlton
¹
,
Lederman
²

2001
Phys. Rev. B