Exchange bias and two steps magnetization reversal in porous Co/CoO layer

Ovejero, Jesús G.; Godinho, Vanda; Lacroix, Bertrand; García, M. A.; Hernando, A.; Fernández, A.

doi:10.1016/j.matdes.2019.107691

Cited by 13 publications

(11 citation statements)

References 49 publications

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“…Furthermore, the exchange bias is found to increase with an increase in Mn amount in the NPs. The exchange bias values of Co@CoO core@shell dispersed in the Cu x O matrix (7780 Oe), porous Co/CoO composites (2800 Oe), MnO dispersed in Co (130 Oe), CoPt/CoO (1730 Oe), NiCo/NiCoO (anomalous behavior from +300 to −700 Oe depending on the oxygen amount), LaSrMnO 3 :NiO (260 Oe), α-Cr 2 O 3 @α-Fe 0.40 Cr 1.60 O 2.92 (362 Oe), Fe 3 O 4 @NiO (145 Oe), FePt@Mn x O y (about 150 Oe), and FePt@CoO (about 400 Oe) , were reported. Some system of proximity of ferromagnetics and antiferromagnetics such as Fe 3 O 4 @γ-Mn 2 O 3 and FePt@NiO did not show exchange bias. , This may be due to the low crystalline anisotropy effect from antiferromagnetic Mn 2 O 3 or NiO that could not lead unidirectional anisotropy spins.…”

Section: Results and Discussionmentioning

confidence: 99%

“…There are reports on exchange bias phenomena in core@shell such as Co@CoO and composites such as NiCo/NiCoO, Co/CoN, Co/MnO, Co 80 Ni 20 /oxide, CoPt/CoO, Fe 3 O 4 /FeO, LaSrMnO 3 /NiO, Fe/γ-Fe 2 O 3 , Fe/Fe x O, Ni/NiO, Cr 2 O 3 /CrO 2 , FeCo/CoFeO, FePt/MnO, FePt/Fe 3 O 4 , CoFe 2 O 4 @Mn, and Mn/Mn 3 O 4 . − The study shows the dependence of exchange bias ( H EB ) on temperature ( T ) where n = 1/2, 3/2... This suggests that H EB decreases with an increase in temperature, and also, it is dependent on power ( n ).…”

Section: Introductionmentioning

confidence: 99%

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Insights into the Structural and Microscopic Origin of Magnetic Properties of the γ-Fe₂O₃@Mn_xO_y Nanostructure

et al. 2021

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Hetero-nanostructures having multi-layered ferromagnetic–antiferromagnetic ultrathin films, dispersion of ferromagnetic particles to the antiferromagnetic matrix, and a core–shell model (F@AF) can exhibit an exchange bias (H EB) that will be useful for spintronic materials such as spin valves, magnetic random-access memories, and ultrahigh data storage. The spin proximity effect of F and AF in the monodispersed core–shell is not much reported. For the first time, we report the preparation of core–shell monodispersed nanoparticles of γ-Fe2O3@Mn x O y having different thicknesses of shells. The microscopic origin of magnetic properties and the microscopic crystal structure are explained by experimental results such as energy-dispersive analysis of X-rays line scanning, X-ray absorption near-edge spectroscopy, and magnetic data. The values of H EB for γ-Fe2O3@Mn x O y (Mn6) and γ-Fe2O3@Mn x O y (Mn12) are found to be 8 and 79 Oe, respectively. Also, possible theoretical models such as crystal field stabilization energy for normal or inverse spinel structures and possible magnetic proximity interactions in core@shell models are discussed. Interestingly, samples show the heating behavior required for hyperthermia under an AC magnetic field, and materials will be potential for hyperthermia cancer therapy. Thermal decomposition of γ-Fe2O3@Mn x O y produces α-Fe2–2x Mn2x O3 at 550 °C, but their unit cell volumes are almost the same even after occupancy of 12 at. % Mn3+ in Fe3+ sites, and the origin of this behavior is explained for the first time.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Insights into the Structural and Microscopic Origin of Magnetic Properties of the γ-Fe₂O₃@Mn_xO_y Nanostructure

et al. 2021

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“…Since then, the exchange coupling mechanism has been studied in a number of different systems (NPs, films and patterned structures) consisting of at least two magnetic phases with different intrinsic anisotropy and, in many cases, also with different magnetic nature (ferromagnetic, antiferromagnetic, ferrimagnetic). The exchange anisotropy is also responsible for the exchange bias effect [ 61 , 62 , 63 , 64 , 65 ], i.e., the horizontal shift of the hysteresis loop, particularly interesting for technological applications in spintronic devices [ 66 ].…”

Section: Core/shell Nanoparticles (Cs_nps)mentioning

confidence: 99%

Nanoparticles for Magnetic Heating: When Two (or More) Is Better Than One

et al. 2021

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The increasing use of magnetic nanoparticles as heating agents in biomedicine is driven by their proven utility in hyperthermia therapeutic treatments and heat-triggered drug delivery methods. The growing demand of efficient and versatile nanoheaters has prompted the creation of novel types of magnetic nanoparticle systems exploiting the magnetic interaction (exchange or dipolar in nature) between two or more constituent magnetic elements (magnetic phases, primary nanoparticles) to enhance and tune the heating power. This process occurred in parallel with the progress in the methods for the chemical synthesis of nanostructures and in the comprehension of magnetic phenomena at the nanoscale. Therefore, complex magnetic architectures have been realized that we classify as: (a) core/shell nanoparticles; (b) multicore nanoparticles; (c) linear aggregates; (d) hybrid systems; (e) mixed nanoparticle systems. After a general introduction to the magnetic heating phenomenology, we illustrate the different classes of nanoparticle systems and the strategic novelty they represent. We review some of the research works that have significantly contributed to clarify the relationship between the compositional and structural properties, as determined by the synthetic process, the magnetic properties and the heating mechanism.

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“…[ 13,22–26 ] In the CoO‐based FM/AFM films, enhanced exchange bias coupling was recently realized via employing a porous structure or strong magnetocrystalline anisotropy FM layer. [ 11,27 ] Thus, the strong exchange bias and strain‐tuning effect in polycrystalline FM/AFM systems are critical for flexible spintronics.…”

Section: Introductionmentioning

confidence: 99%

“…Some flexible FM/AFM films were successfully realized via these approaches, such as NiMn/Fe 4 N, BiFeO 3 /La 0.7 Sr 0.3 MnO 3 , C o / C o O , etc. [10][11][12][13][14][15][16] The reported FM/AFM films not only exhibit decent mechanical durability but also have tunable magnetic properties. For instance, large strain can be induced in flexible FM/AFM film through large curvature bending, [12,15] whereas the induced strain in the rigid counterparts is usually small.…”

Section: Introductionmentioning

confidence: 99%

Large and Robust Exchange Bias in Co/CoO film: Implication for Flexible Spintronics

Sun

Tang

Chen

et al. 2022

Advanced Physics Research

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Developing a robust and flexible exchange bias (EB) system is crucial for wearable spintronic devices. In this work, large and robust EB effect is demonstrated in flexible Co/CoO thin films grown by magnetron sputtering. The obtained EB field is as large as 6172 Oe at low temperatures on a flexible substrate. Based on the atomistic spin models, the unexpectedly large EB field is explained by the decrease of ferromagnetic grain size and the increase of ferromagnetic /antiferromagnetic contact area. Furthermore, the strain-dependent coercivity and EB effect are observed in flexible Co/CoO films. Finally, the flexible Co/CoO thin film shows no degradation (even a slight increase) of performances in all figures of merit after 500 bending cycles, indicating excellent mechanical durability. This study sheds light on Co/CoO as a robust EB material for flexible spintronics.

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Exchange bias and two steps magnetization reversal in porous Co/CoO layer

Cited by 13 publications

References 49 publications

Insights into the Structural and Microscopic Origin of Magnetic Properties of the γ-Fe₂O₃@Mn_xO_y Nanostructure

Insights into the Structural and Microscopic Origin of Magnetic Properties of the γ-Fe₂O₃@Mn_xO_y Nanostructure

Nanoparticles for Magnetic Heating: When Two (or More) Is Better Than One

Large and Robust Exchange Bias in Co/CoO film: Implication for Flexible Spintronics

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Exchange bias and two steps magnetization reversal in porous Co/CoO layer

Cited by 13 publications

References 49 publications

Insights into the Structural and Microscopic Origin of Magnetic Properties of the γ-Fe2O3@MnxOy Nanostructure

Insights into the Structural and Microscopic Origin of Magnetic Properties of the γ-Fe2O3@MnxOy Nanostructure

Nanoparticles for Magnetic Heating: When Two (or More) Is Better Than One

Large and Robust Exchange Bias in Co/CoO film: Implication for Flexible Spintronics

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Insights into the Structural and Microscopic Origin of Magnetic Properties of the γ-Fe₂O₃@Mn_xO_y Nanostructure

Insights into the Structural and Microscopic Origin of Magnetic Properties of the γ-Fe₂O₃@Mn_xO_y Nanostructure