Exchange bias in ferromagnet/antiferromagnet bilayers

Shi, Zhong; Du, Jun; Zhou, Sheng

doi:10.1088/1674-1056/23/2/027503

Cited by 27 publications

(25 citation statements)

References 97 publications

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“…Interestingly, both parameters show nonmonotonic trend with d AFM , as they exhibit a maximum for CS9 ( d AFM = 5 nm) and a subsequent decay to a value that remains constant for the two larger samples (CS15 and CS18). Regarding H E , its dependence is in good agreement with that theoretically predicted , and experimentally observed ,, in AFM|FM bilayers. The nonmonotonic dependence is described by considering the concomitant effect of the energy barrier of the AFM material ( K AFM V AFM ) and the formation and growth of AFM domains, which are responsible for the onset and the maximum of H E , respectively. , However, due to the reduced volume of our CS NPs, the formation and growth of AFM domains appears rather unlikely.…”

Section: Resultssupporting

confidence: 89%

Strongly Exchange Coupled Core|Shell Nanoparticles with High Magnetic Anisotropy: A Strategy toward Rare-Earth-Free Permanent Magnets

et al. 2016

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Antiferromagnetic(AFM)|ferrimagnetic(FiM) core|shell (CS) nanoparticles (NPs) of formula Co0.3Fe0.7O|Co0.6Fe2.4O4 with mean diameter from 6 to 18 nm have been synthesized through a one-pot thermal decomposition process. The CS structure has been generated by topotaxial oxidation of the core region, leading to the formation of a highly monodisperse single inverted AFM|FiM CS system with variable AFM-core diameter and constant FiM-shell thickness (∼2 nm). The sharp interface, the high structural matching between both phases, and the good crystallinity of the AFM material have been structurally demonstrated and are corroborated by the robust exchange-coupling between AFM and FiM phases, which gives rise to one among the largest exchange bias (H E) values ever reported for CS NPs (8.6 kOe) and to a strongly enhanced coercive field (H C). In addition, the investigation of the magnetic properties as a function of the AFM-core size (d AFM), revealed a nonmonotonous trend of both H C and H E, which display a maximum value for d AFM = 5 nm (19.3 and 8.6 kOe, respectively). These properties induce a huge improvement of the capability of storing energy of the material, a result which suggests that the combination of highly anisotropic AFM|FiM materials can be an efficient strategy toward the realization of novel rare-earth-free permanent magnets.

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Section: Resultssupporting

confidence: 89%

Strongly Exchange Coupled Core|Shell Nanoparticles with High Magnetic Anisotropy: A Strategy toward Rare-Earth-Free Permanent Magnets

et al. 2016

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“…The EB effect was discovered in 1956 by Meiklejohn and Bean in Co/CoO nanoparticles1, and has been extensively studied and explored in various systems including FM-AFM nanocomposite/bilayers2, spin glass (SG)-FM structures3, and more45. These systems have significant applications in ultrahigh-density magnetic recording, giant magnetoresistance, and spin valve devices678.…”

mentioning

confidence: 99%

Giant spontaneous exchange bias triggered by crossover of superspin glass in Sb-doped Ni50Mn38Ga12 Heusler alloys

Tian

Cao

Zhang

et al. 2016

Sci Rep

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A spontaneous exchange bias (SEB) discovered by Wang et al. [Phys. Rev. Lett. 106 (2011) 077203.] after zero-field cooling (ZFC) has attracted recent attention due to its interesting physics. In this letter, we report a giant SEB tuned by Sb-doping in Ni50Mn38Ga12-xSbx Heusler alloys. Such an SEB was switched on below the blocking temperature of approximately 50 K. The maximum exchange bias HE can arrive at 2930 Oe in a Ni50Mn38Ga10Sb2 sample after ZFC to 2 K. Further studies showed that this SEB was attributable to interaction of superspin glass (SSG) and antiferromagnetic matix, which was triggered by the crossover of SSG from canonical spin glass to a cluster spin glass. Our results not only explain the underlying physics of SEB, but also provide a way to tune and control the SEB performance.

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“…1 In thin-film exchange-biased systems, it has been shown that the magnitude of the exchange bias is conditional on the relative thicknesses of each thin-film layer; exchange bias is known to be inversely proportional to the FM thickness (reaching a maximum at sub-10 nm film thicknesses). 3,4 The role of the AF thickness on exchange bias is much more complex. 1,3,4 While studied extensively in oxide-coated particles and two-dimensional (2D) bilayer thin-film systems, research into the exchange-bias effect in bulk nanocomposite systems has been limited.…”

Section: Introductionmentioning

confidence: 99%

Exchange Bias in Bulk α-Fe/γ-Fe₇₀Mn₃₀ Nanocomposites for Permanent Magnet Applications

McDonald

Jamer

Krycka

et al. 2019

ACS Appl. Nano Mater.

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Here we report on the microstructural factors influencing the formation of the interfacial exchange bias effect in three-dimensional transition-metal-based nanocomposite systems, with relevance to permanent magnet applications. Bulk phase-separated nanocomposites consisting of the ferromagnetic α-Fe and metastable antiferromagnetic γ-Fe 70 Mn 30 phases exhibit a notable low-temperature exchange bias and substantial coercivity (H ex = 24.6 kA/m, H C = 95.7 kA/m) as well as a near room-temperature blocking temperature. Structural investigation by synchrotron X-ray diffraction, neutron scattering, and transmission electron microscopy confirm that the ferromagnetic α-Fe phase nucleates as small precipitates (d ≈ 50 nm) at the grain boundaries of the antiferromagnetic γ-Fe 70 Mn 30 grains (d = 360−740 nm) and grows anisotropically upon heat treatment, resulting in an elliptical geometry. These results indicate that optimization of the exchange bias effect in bulk nanocomposite systems may be achieved through maximizing the surface-to-volume ratio of ferromagnetic precipitates in an antiferromagnetic matrix, enhancing the magnetocrystalline anisotropy of the antiferromagnetic phase to facilitate interfacial pinning and ensuring a balanced distribution of the ferromagnetic and antiferromagnetic phases. This work further clarifies critical factors influencing the formation of an exchange bias in an inexpensive transition-metal-based bulk nanocomposite system with potential for scalable production.

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Exchange bias in ferromagnet/antiferromagnet bilayers

Cited by 27 publications

References 97 publications

Strongly Exchange Coupled Core|Shell Nanoparticles with High Magnetic Anisotropy: A Strategy toward Rare-Earth-Free Permanent Magnets

Strongly Exchange Coupled Core|Shell Nanoparticles with High Magnetic Anisotropy: A Strategy toward Rare-Earth-Free Permanent Magnets

Giant spontaneous exchange bias triggered by crossover of superspin glass in Sb-doped Ni50Mn38Ga12 Heusler alloys

Exchange Bias in Bulk α-Fe/γ-Fe₇₀Mn₃₀ Nanocomposites for Permanent Magnet Applications

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Exchange bias in ferromagnet/antiferromagnet bilayers

Cited by 27 publications

References 97 publications

Strongly Exchange Coupled Core|Shell Nanoparticles with High Magnetic Anisotropy: A Strategy toward Rare-Earth-Free Permanent Magnets

Strongly Exchange Coupled Core|Shell Nanoparticles with High Magnetic Anisotropy: A Strategy toward Rare-Earth-Free Permanent Magnets

Giant spontaneous exchange bias triggered by crossover of superspin glass in Sb-doped Ni50Mn38Ga12 Heusler alloys

Exchange Bias in Bulk α-Fe/γ-Fe70Mn30 Nanocomposites for Permanent Magnet Applications

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Exchange Bias in Bulk α-Fe/γ-Fe₇₀Mn₃₀ Nanocomposites for Permanent Magnet Applications