Cooling-field dependence of dipole-induced loop bias

Hu, Yong; Lü, Qiang; Chi, Xiaodan; Zhang, Zibo; Hu, Tianyi; Li, Ruijun; Yu, Lili; Du, An

doi:10.1088/1361-6528/ab1a57

Cited by 7 publications

(9 citation statements)

References 57 publications

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“…The issue of the cooling field impact on the magnitude and sign of the exchange bias field has been recently raised in a few research papers. However, these works focused on AFM/FM bilayer, 27 spin glass/FM interface, 28 or a system where AFM and FM layers are separated by a paramagnetic material. 29 This paper develops this field of research further by combining two magnetic effects in one study—exchange bias and magnetic exchange spring—to find how they affect the reversal process.…”

Section: Introductionmentioning

confidence: 99%

Magnetization Reversal Mechanism in Exchange-Biased Spring-like Thin-Film Composite

Perzanowski

Zarzycki

Gregor-Pawlowski

et al. 2020

ACS Appl. Mater. Interfaces

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Development of modern spintronic devices requires materials exhibiting specific magnetic effects. In this paper, we investigate a magnetization reversal mechanism in a [Co/Pd x ] 7 /CoO/[Co/Pd y ] 7 thin-film composite, where an antiferromagnet is sandwiched between a hard and a soft ferromagnets with different coercivities. The antiferromagnet/ferromagnet interfaces give rise to the exchange bias effect. The application of soft and hard ferromagnetic films causes exchange-spring-like behavior, while the choice of the Co/Pd multilayers provides large out-of-plane magnetic anisotropy. We observed that the magnitude and the sign of the exchange bias anisotropy field are related to the arrangement of the magnetic moments in the antiferromagnetic layer. This ordering is induced by the spin orientation present in neighboring ferromagnetic films, which is, in turn, dependent on the orientation and strength of the external magnetic field.

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Section: Introductionmentioning

confidence: 99%

Magnetization Reversal Mechanism in Exchange-Biased Spring-like Thin-Film Composite

Perzanowski

Zarzycki

Gregor-Pawlowski

et al. 2020

ACS Appl. Mater. Interfaces

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“…Similarly, experimentally the EB can be regulated in the real materials CoFe/FeMn/CoFe trilayers depending on thicknesses of the seed CoFe layer and the FeMn layer, while it is independent of the thickness of the target CoFe layer [42]. Actually, the antiferromagnetic layer thickness determines the antiferromagnetic anisotropy energy [20], and thus changing K AF in the literature [42] can be considered approximatively due to change of the antiferromagnetic layer thickness experimentally.…”

Section: Resultsmentioning

confidence: 89%

“…The effects of dipole interactions of ferromagnet and ferromagnet/antiferromagnet interface on the magnetization behaviors have been discussed in our previous papers [20]. Meanwhile, one [21] has suggested that the dipole interaction of antiferromagnet affects only quantitatively rather than qualitatively the symmetry breaking in a thin antiferromagnetic layer.…”

Section: Model and Monte-carlo Simulationmentioning

confidence: 94%

Improvement and stabilization of exchange bias in ferromagnet/antiferromagnet/ferromagnet trilayers

Chi

2020

Nanotechnology

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Exchange bias (EB) in ferromagnet/antiferromagnet bilayers, which has been extensively studied and applied for several decades, is sensitive to many factors such as layer thickness, texture and crystallization. Various factors in an antiferromagnet may counterbalance each other to limit and deteriorate EB. We used an unbiased Monte-Carlo method based on a modified Metropolis algorithm to predict that dependence of EB properties on antiferromagnetic anisotropy (KAF) are highly improved by attaching a soft ferromagnet on the other side of the antiferromagnet. On one hand, target ferromagnet in trilayers displays a pronounced and stabilized EB plateau at high KAF, on the contrary, EB is completely removed and instead a high coercivity is observed at low KAF, exhibiting a roughly KAF-modulated EB switching effect. On the other hand, EB is identified with no training in trilayers and well axially symmetric about antiferromagnetic easy axis. Meanwhile, in trilayers EB versus angle (θ) which is between antiferromagnetic easy axis and the direction of magnetic field is a roughly linear relationship in the intermediate θ range. Microscopic explorations found that a fully uncompensated magnetization in antiferromagnet may appear in trilayers and its rotatability is precisely controlled by KAF, designating that the antiferromagnet/seed-ferromagnet bilayers resemble a ferromagnet with changeable hardness to induce a maximized coercivity of target ferromagnet at low KAF to a maximized EB at high KAF. Finally, a phenomenological model reveals that antiferromagnetic spins change from a fluctuated state to a blocked state due to the existence of seed ferromagnet, and thus in this work we conceived an artificial pinning layer to establish and regulate EB.

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“…The ferromagnet/antiferromagnet interfacial dipolar constant (D IF ) is unknown experimentally, while it is adjustable by changing the spacer thickness [31,32], and according to the reduced magnetic moment set in the antiferromagnetic layer, a smaller value of D IF compared to D FM is used (D IF = 0.4D FM ), which guarantees induction of exchange bias [34]. We employed the image-sum method in the film plane to avoid the drastic effects produced by truncating dipolar interactions [34,38].…”

Section: Model and Monte Carlo Methodsmentioning

confidence: 99%

“…However, when considering largearea ferromagnetic domains, or so-called surplus magnetization, commonly induced at the interface between paramagnetic and antiferromagnetic layers [31], between paramagnetic and ferromagnetic layers [32], or on the surface of nanoparticles [33] as building blocks instead of atoms, the dipolar interaction energy can be orders of magnitude larger. Hu et al [34] used Monte Carlo simulations to reproduce and interpret the cooling -field dependence of the exchange bias field induced by dipolar interactions. Further, they also predicted that a long-range exchange bias field may emerge in the ferromagnet/antiferromagnet core/shell structure.…”

Section: Introductionmentioning

confidence: 99%

Temperature dependence of dipole-induced exchange bias

Lü

Hu²

2020

Nanotechnology

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A modified Monte Carlo method is used to study the dependence of exchange bias, induced by long-range ferromagnet/antiferromagnet interfacial dipolar interactions, on temperature after field cooling. Since sufficient nonzero surplus magnetization in the antiferromagnetic layer is preserved, a positive exchange bias field is yielded. Significantly, this exchange field increases with decreasing temperature and may level off at low temperatures. Then, the antiferromagnetic anisotropy constant, easy-axis direction with respect to the cooling-field direction, antiferromagnetic exchange constant, and antiferromagnetic layer thickness were modulated to study their roles in establishing the low-temperature plateau-like exchange bias field. A thick enough antiferromagnetic layer with the easy-axis direction aligning with the cooling field maximizes the plateau height with a large antiferromagnetic anisotropy constant, while a small antiferromagnetic exchange constant greatly widens the plateau, even from the exchange bias blocking temperature to the lowest temperature. On explicitly calculating the surplus magnetization values in the antiferromagnetic layer meanwhile the dipolar and Zeeman energies in the antiferromagnetic layer, it is found that the ferromagnet/antiferromagnet interfacial dipolar interactions are predominant at the descending branch of the loop to suppress the coercive field with decreasing temperature; in contrast, the magnetic field takes over the lead at the ascending branch and monotonically enhances the coercive field, at the same pace as the decrease in the coercive field at the descending branch. As a consequence, the loop retains a constant shift and becomes wider with decreasing temperature. The long-range noncontact exchange bias that is insensitive to temperature may be used to develop thermal-agitation-resistant spintronic devices with unidirectional anisotropy.

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Cooling-field dependence of dipole-induced loop bias

Cited by 7 publications

References 57 publications

Magnetization Reversal Mechanism in Exchange-Biased Spring-like Thin-Film Composite

Magnetization Reversal Mechanism in Exchange-Biased Spring-like Thin-Film Composite

Improvement and stabilization of exchange bias in ferromagnet/antiferromagnet/ferromagnet trilayers

Temperature dependence of dipole-induced exchange bias

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