Exchange bias of the interface spin system at the Fe/MgO interface

Fan, Yabin; Smith, K.; Lüpke, G.; Hanbicki, A. T.; Goswami, R.; Li, C. H.; Zhao, Hui; Jonker, B. T.

doi:10.1038/nnano.2013.94

Cited by 102 publications

(87 citation statements)

References 48 publications

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“…The loss of spin filtering would be related to the Verwey transition (expected at T V ∼ 120 K) in which Fe 3 O 4 goes from insulator below T V to semiconductor. This FeO X layer has been reported to form at the interface between Fe and MgO, even in high-vacuum conditions, due to Fe-O bonding [24]. Although in Fe/MgO/Fe systems the FeO X layer is suppressed by appropriate annealing treatments, in our case an enhancement of the FeO X layer after annealing is detected, thus suggesting that the LSMO layer may well act as an extra source of oxygen for the oxidation of the Fe interface.…”

Section: Discussioncontrasting

confidence: 40%

“…The existence of FeO X at the interface has been reported in several cases, showing that its amount depends critically on the MgO growth method. FeO X has been shown to form at the interface between Fe and MgO due to Fe-O bonding [24]. The detrimental effect of this FeO X layer on the TMR response, and its improvement after different thermal annealing treatments, has also been previously reported [25].…”

Section: Resultsmentioning

confidence: 80%

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Interfacial effects on the tunneling magnetoresistance inLa0.7Sr0.3MnO3/<

et al. 2015

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We report on magnetotransport properties on La 0.7 Sr 0.3 MnO 3 /MgO/Fe tunnel junctions grown epitaxially on top of (001)-oriented SrTiO 3 substrates by sputtering. It is shown that the magnetoresistive response depends critically on the MgO/Fe interfacial properties. The appearance of an FeO X layer by the interface destroys the 1 symmetry filtering effect of the MgO/Fe system and only a small negative tunneling magnetoresistance (TMR) (∼ −3 %) is measured. However, in annealed samples a switchover from positive TMR (∼ +25% at 70 K) to negative TMR (∼ −1 %) is observed around 120 K. This change is associated with the transition from semiconducting at high T to insulating at low T taking place at the Verwey transition (T V ∼ 120 K) in Fe 3 O 4 , thus suggesting the formation of a very thin slab of magnetite at the MgO/Fe interface during annealing treatments. These results highlight the relevance of interfacial properties on the tunneling conduction process and how it can be substantially modified through appropriate interface engineering.

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Section: Discussioncontrasting

confidence: 40%

Section: Resultsmentioning

confidence: 80%

Interfacial effects on the tunneling magnetoresistance inLa0.7Sr0.3MnO3/<

et al. 2015

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“…On the contrary, for a semiconducting or insulating spacer [3][4][5][6][7][8], magnetic properties seem to depend deeply on growth conditions and then on structural specifications. Among them, the MgO spacer [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] appears unique in presenting a large variety of experimental results. They concern either the MgO thickness range and the coupling sign and strength, or the junction magnetic geometry (planar or perpendicular magnetization).…”

Section: Introductionmentioning

confidence: 99%

Metalliclike behavior of the exchange coupling in (001) Fe/MgO/Fe junctions

et al. 2017

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Exchange magnetic coupling between Fe electrodes through a thin MgO interlayer in epitaxial junctions has been investigated as a function of temperature, MgO thickness, and interface quality. Depending on the MgO thickness, which has been varied from 1.5 to 4 monolayers, two opposite temperature dependences are clearly disentangled. For a thin MgO spacer, the main component decreases with temperature following a metalliclike behavior. On the contrary, for the thickest MgO layers, the main component increases with temperature, following an Arrhenius law. Moreover, the insertion of a monoatomic roughness at the bottom MgO interface, induced by the addition of a fraction of a Fe monolayer, exacerbates the metallic features as an oscillatory behavior from antiferromagnetic to ferromagnetic is observed. These results allow questioning the simple tunneling mechanism usually invoked for MgO coupling, and suggest a crossover behavior of the thin MgO spacer from metallic to insulating with a progressive opening of the gap.

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“…But these are usually associated with interface between FM/AFM or FM/ferrimagnetic materials, which is not the case here. However, one recent work [29] is worth mentioning here. An H EB of $19 Oe is reported for a Fe/MgO sample.…”

Section: Introductionmentioning

confidence: 99%

Positive exchange bias in epitaxial permalloy/MgO integrated with Si (100)

Rao

Prater

et al. 2014

Current Opinion in Solid State and Materials Science

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a b s t r a c tIn magnetic random access memory (MRAM) devices, soft magnetic thin film elements such as permalloy (Py) are used as unit cells of information. The epitaxial integration of these elements with the technologically important substrate Si (1 0 0) and a thorough understanding of their magnetic properties are critical for CMOS-based magnetic devices. We report on the epitaxial growth of Ni 82.5 Fe 17.5 (permalloy, Py) on Si (1 0 0) using a TiN/MgO buffer layer. Initial stages of growth are characterized by the formation of discrete islands that gradually merge into a continuous film as deposition times are extended. Interestingly, we find that the magnetic features of Py films in early stages of island coalescence are distinctly different from the films formed initially (discrete islands) and after extended deposition times (narrow distribution of equiaxed granular films). Isothermal in-plane and out-of-plane magnetic measurements performed on these transitional films show highly anisotropic magnetic behavior with an easy magnetization axis lying in the plane of the film. Importantly, when this sample is zero-field cooled, a positive exchange bias and vertical loop shift are observed, unusual for a soft ferromagnet like Py. Repeated field cycling and hysteresis loops up to the fields of 7T produced reproducible hysteresis loops indicating the existence of strongly pinned spin configurations. Classical interface related exchange bias models cannot explain the observed magnetic features of the transitional Py films. We believe that the anomalous magnetic behavior of such Py films may be explained by considering the highly irregular morphology that develops at intermediate growth times that are possibly also undergoing a transition from Bloch to Neel domain wall structures as a function of Py island size. This study broadens the current understanding of magnetic properties of Py thin layers for technological applications in magneto-electronic devices, integrated with Si (1 0 0). Ó 2014 Elsevier Ltd. All rights reserved.Motivated by the proposed racetrack memory patented [1] by Parkin et al, a great deal of research activity has been devoted to Permalloy (Py) magnetic nanostructures for high frequency applications. Py usually refers to Ni 1Àx Fe x alloys that have a vanishingly small magnetocrystalline anisotropy and magnetostriction but extremely large magnetic permeability. These unique properties make Py one of the most important soft magnets for a variety of applications, such as free layers in spin-valve magnetic-reading heads [2,3]. The Py/MgO combination has been widely used in magnetic tunnel junctions (MTJs) devices. More recently, Py is being extensively used [4,5] to demonstrate electric field control of ferromagnetism (FM) in multiferroic based devices. Hence, exploring and understanding the magnetic properties of Py when interfaced with magnetic/non-magnetic oxide materials is of primary importance.To date, epitaxial Py layers have been deposited [6] on MgO bulk substrates using molecular beam...

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Exchange bias of the interface spin system at the Fe/MgO interface

Cited by 102 publications

References 48 publications

Interfacial effects on the tunneling magnetoresistance inLa0.7Sr0.3MnO3/<

Interfacial effects on the tunneling magnetoresistance inLa0.7Sr0.3MnO3/<

Metalliclike behavior of the exchange coupling in (001) Fe/MgO/Fe junctions

Positive exchange bias in epitaxial permalloy/MgO integrated with Si (100)

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