Fabrication of Magnetic Tunneling Junctions with NaCl Barriers

Nakazumi, Makoto; Yoshioka, Daichi; Yanagihara, Hideto; Kita, Eiji; Koyano, Tomohiro

doi:10.1143/jjap.46.6618

Cited by 13 publications

(4 citation statements)

References 15 publications

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“…For example, a MTJ with a single-crystal NaCl barrier, which has an identical crystal structure and also a markedly similar band structure to that of MgO, has been reported. 23 Another example are MTJs based on single crystal MgAl 2 O 4 barrier with the spinel structure, where Heusler alloy electrodes were used. 18,24 A Mg-B-O barrier was also investigated, where a CoFeB layer was used for one of the FM electrodes.…”

Section: Mgo-based Magnetic Tunnel Junctionsmentioning

confidence: 99%

Interface Characterization of Epitaxial Fe/MgO/Fe Magnetic Tunnel Junctions

Wang¹,

Ward²,

Hesjedal³

et al. 2012

j nanosci nanotechnol

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Following predictions by first-principles theory of a huge tunnel magnetoresistance (TMR) effect in epitaxial Fe/MgO/Fe magnetic tunnel junctions (MTJs), measured magnetoresistance (MR) ratios of about 200% at room temperature (RT) have been reported in MgO-based epitaxial MTJs. Recently, a MR ratio of about 600% has been reported at RT in MgO-based MTJs prepared by magnetron sputtering, using amorphous CoFeB as the ferromagnetic electrode. These MTJs show great potential for application in spintronic devices. Fully epitaxial MTJs are excellent model systems that enhance our understanding of the spin-dependent tunneling process as the interface is well defined and can be fully characterized. Both theoretical calculations and experimental results clearly indicate that the interfacial structure plays a crucial role in the coherent tunneling across a single crystal MgO barrier, especially in epitaxial MgO-based MTJs grown by molecular beam epitaxy (MBE). Surface X-ray diffraction, Auger electron spectroscopy, X-ray absorption spectra, and X-ray magnetic circular dichroism techniques have been reported previously for interface characterization. However, no consistent viewpoint has been reached on the interfacial structures (such as FeO layer formation at the bottom Fe/MgO interface), and it is still an open issue. In this article, our recent studies on the interface characterization of MgO-based epitaxial MTJs by X-ray photoelectron spectroscopy, high resolution transmission electron microscopy, and spin-dependent tunneling spectroscopy, will be presented.

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Section: Mgo-based Magnetic Tunnel Junctionsmentioning

confidence: 99%

Interface Characterization of Epitaxial Fe/MgO/Fe Magnetic Tunnel Junctions

Wang¹,

Ward²,

Hesjedal³

et al. 2012

j nanosci nanotechnol

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“…Recent band structure calculations by Vlaic [7] predicted a high tunnel magnetoresistance (TMR) ratio for Fe/NaCl/Fe(001) magnetic tunnel junctions (MTJs), but the experimental realization of such devices has been unsuccessful due to difficulties in sample preparation [8]. The growth of NaCl on iron is difficult to improve, probably because of corrosion of the substrate by NaCl during deposition or annealing of the system at elevated temperatures.…”

Section: Introductionmentioning

confidence: 99%

Layer-by-layer growth of sodium chloride overlayers on an Fe(001)-p(1 × 1)O surface

et al. 2012

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Ultra-thin NaCl films epitaxially grown on an Fe(001)-p(1 × 1)O surface have been investigated in ultra-high vacuum by non-contact atomic force microscopy and low energy electron diffraction. It has been found that at temperatures below 145 °C NaCl initially grows as monoatomic thick islands on substrate terraces, while at temperatures above 175 °C biatomic thick islands are also formed at substrate step edges. Both types of islands have the same Fe(001)-O[100] [parallel] NaCl(001)[110] orientation, leading to a (4 × 4) superstructure, where the NaCl unit cell is oriented at 45° with respect to the substrate. Interestingly, no c(2 × 2) superstructure with the NaCl unit cell oriented at 0° has been observed. The oxygen on the iron surface promotes layer-by-layer growth, resulting in atomically flat films with 40-60 nm wide terraces at coverages ranging from 0.75 to 12 ML. Such NaCl films are of much higher quality than MgO films grown on Fe(001) and Fe(001)-p(1 × 1)O surfaces and represent a unique epitaxial system of an alkali halide on a pure metallic substrate. The reduced number of defects and the layer-by-layer mode of growth make this system very attractive for applications where an atomically defined tunnel barrier is required to control the properties of a device.

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“…Beside the above-mentioned Fe/MgO/Fe MTJs, recent experimental data revealed the possibility of fabrication of novel tunnel junctions with monocrystalline NaCl (0 0 1) barriers [10]. Even at this stage the fabrication of single-crystalline Fe/NaCl/Fe (0 0 1) junctions was hindered by the large difference in the surface free energy between Fe and NaCl, the epitaxial Fe/NaCl/Fe (0 0 1) structure identifies as a new system suitable for a comparative study of the magnetic and transport properties.…”

Section: Introductionmentioning

confidence: 99%

Calculated magnetic and transport properties of Fe/Nacl/Fe (001) magnetic tunnel junction

Vlaic

2010

Journal of Magnetism and Magnetic Materials

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Fabrication of Magnetic Tunneling Junctions with NaCl Barriers

Cited by 13 publications

References 15 publications

Interface Characterization of Epitaxial Fe/MgO/Fe Magnetic Tunnel Junctions

Interface Characterization of Epitaxial Fe/MgO/Fe Magnetic Tunnel Junctions

Layer-by-layer growth of sodium chloride overlayers on an Fe(001)-p(1 × 1)O surface

Calculated magnetic and transport properties of Fe/Nacl/Fe (001) magnetic tunnel junction

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