Observation of the Exchange Interaction at the Surface of a Ferromagnet

Mauri, D.; Scholl, D.; Hc, Siegmann; Kay, E.

doi:10.1103/physrevlett.61.758

Cited by 87 publications

(41 citation statements)

References 12 publications

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“…The parameter ␣ is generally larger for the surface than the bulk due to surface exchange softening. 26 From Table II, the magnitude of ␣ is 2.1ϫ 10 −5 K −3/2 and 1.4ϫ 10 −5 K −3/2 for type 1 and type 2 MTJ samples, respectively. The values have the same order of magnitude with most amorphous alloys.…”

Section: Discussionmentioning

confidence: 94%

“…The parameter ␣ is generally larger for the surface than the bulk due to surface exchange softening. 26 The parameter P 0 is sensitive to disorder and defects in the FM electrodes and FM/I interface. These disorder and defects could be due to interdiffusion at the interface, interface roughness, impurities, and grain boundaries, etc.…”

Section: B Voltage Dependence Of Conductancementioning

confidence: 99%

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Temperature dependence of magnetoresistance in magnetic tunnel junctions with different free layer structures

2006

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The temperature and bias voltage dependence of magnetoresistance and the resistance of two types of magnetic tunnel junction ͑MTJ͒ samples were studied. These two types of MTJ samples have different free layer structures, while having the same pinned layer structures and with the same material for free and reference layers. The layer structure for type 1 MTJs is 80Ru-8CoFeB-15Al 2 O 3 -50CoFeB-9Ru-54FeCo-350CrMnPt ͑in angstroms͒. The layer structure for type 2 MTJs is 80Ru-40CoFeB-50RuTa-40CoFeB-15Al 2 O 3 -50CoFeB-9Ru-54FeCo-350CrMnPt. The tunneling magnetoresistance ͑TMR͒ ratio ͓͑R AP -R P ͒ / R P ͔ is about 26% and 69% at room temperature for type 1 and type 2 MTJs, respectively. A TMR as high as 107% has been observed for type 2 MTJ samples at 13 K. By analysis of the voltage and temperature dependence of the resistance and magnetoresistance in these MTJs, we discuss the effects of the magnetic behavior of the free layers, barrier qualities, and barrier interfaces. The results clearly indicate that the micromagnetization orientation at the interface between the free layer and the barrier layer is one of the important factors that determines the TMR ratio.

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Section: Discussionmentioning

confidence: 94%

Section: B Voltage Dependence Of Conductancementioning

confidence: 99%

Temperature dependence of magnetoresistance in magnetic tunnel junctions with different free layer structures

2006

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“…Diese Austauschentartung manifestiert sich augenfallig im Magnetismus der festen Korper. G. [22]. Tatsachlich kann man aus k die Veranderung des quantenmechanischen Austausches in der Oberflache experimentell bestimmen [23].…”

Section: Stall So Ist Der Polarisationsgrad Derunclassified

Spektroskopie mit polarisierten Elektronen

Siegmann¹

1992

Phys. Bl.

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Der Spin des Elektrons spielt eine grundlegende Rolle z. B. in den elektroschwachen Prozessen der Hochenergiephysik oder auch im Magnetismus. Die Spektroskopie der Festkörper mit polarisierten Elektronen ermöglicht es u. a., auch bei Metallen die von der Dispersion der Elektronenzustände abhängige Austauschaufspaltung zu bestimmen und den Magnetismus der durch die Oberfläche induzierten neuen Zustände zu messen. Kaskadenelektronen werden emittiert, wenn man die Oberfläche mit einem primären Elektronenstrahl von einigen keV mit hoher Intensität und Polarisationsgrad bestrahlt. Sie erweisen sich als ideales Hilfsmittel zur Magnetometrie der Oberflächen und der zweidimensionalen magnetischen Systeme.

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“…We note that in obtaining k SL we took into account the energy gap [50] created in the magnon spectra by the MAE-the same applies to the case of bulk Dy. Importantly, the fact that k SL = 3.5 indicates a notable softening of the indirect-exchange coupling transversal to the interfaces [49] in the Dy/Sc SL, as a result of the finite size of the noninteracting Dy layers. An essential feature of RE magnetism is a long spin-spin exchange coupling length ξ which is at least of ∼40 MLs [51].…”

mentioning

confidence: 99%

“…It is found that m s (T ) is well modeled by a modified spin-wave theory [48] [see Fig. 1(d)], which predicts a decay of a surface, or two-dimensional-like, M(T ) according to a pseudo Bloch-T 3/2 power law with a prefactor k s which ranges from 3 to 5.4 [49]. The best-fit prefactor in the Dy/Sc SL is k SL = 3.5, which produces an excellent accord between experiment and theory for t 0.5.…”

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confidence: 99%

Universal scaling of the magnetic anisotropy in two-dimensional rare-earth layers

Benito

Ward

2015

Phys. Rev. B

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Unraveling the influence that low dimensionality has upon the spin's stability in two-dimensional (2D) systems is instrumental for the efficient engineering of energy barriers in ultrathin magnetic layers. Taking rare-earth-based ultrathin multilayered nanostructures as a model system, we have investigated the dissimilar impact that low dimensionality and finite-size effects have upon the magnetic anisotropy energy (MAE) at the nanoscale. We conclusively show that the reduced dimensionality of the spin's system in 2D ferromagnetic layers imprints on the MAE constants a universal temperature decay as a quadratic power law of the reduced magnetization. This result is in agreement with predictions, although in marked contrast to the rank-dependent, thereby faster, decay of the MAE constants observed in three-dimensional nanostructures. [7], and plays an essential part in spin dynamics [8], has gathered huge interest [9,10], being in the spotlight of countless studies aiming to explore and gain control over the MAE of nanometersized matter [11].The relentless trend for miniaturization imposes the shrinking of the device size down to the nanoscale, which entails the arising of dominating surface/interface [12] contributions into MAE. In this way, the symmetry breaking of the lattice potential at the nanosystem boundaries gives rise to huge energy barriers [13,14], which are predominantly contributed by perimeter-edge ions [15]. On the contrary, as layer thickness becomes comparable to the spin-spin exchange range, the magnetic ordering temperatures [16][17][18] are shifted towards lower ones and the spin polarization [19] diminishes faster than in bulk systems as temperature increases. These two facts reflect in the enhancing efficacy of thermally activated spin waves [20] to annihilate long-range magnetic order [21] at the nanoscale.Newly engineered magnetic two-dimensional (2D) hybrid systems [22] have opened up an exciting new route for faster, more power-efficient spintronics [23], albeit they are not exempt from fundamental challenges. Thus, the reduced dimensionality of the crystal field in transition-metal-based nanosystems is well known to revive orbital moments, which contributes to stabilize the magnetic order in nanometer-sized matter [13,24]. However, the impact that the spin's low dimensionality has upon their thermal stability and, therefore, its crucial role in determining their magnetic response, is still poorly understood. The thermal stability of 2D magnets could be elucidated by measuring the temperature scaling of the model-independent MAE in ultrathin layers; nevertheless, such an experimental test has remained elusive upon until now. Here we report on the distinctive way in which finite-size and the spin's dimensionality effects determine the MAE in ultrathin layers. Taking RE superlattices (SLs) as a model system [33], which is featured by the precise modeling of their MAE [29,30], we demonstrate that the two dimensionality of the spin system in ultrathin RE layers imprints a universal, rank-i...

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Observation of the Exchange Interaction at the Surface of a Ferromagnet

Cited by 87 publications

References 12 publications

Temperature dependence of magnetoresistance in magnetic tunnel junctions with different free layer structures

Temperature dependence of magnetoresistance in magnetic tunnel junctions with different free layer structures

Spektroskopie mit polarisierten Elektronen

Universal scaling of the magnetic anisotropy in two-dimensional rare-earth layers

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