Switching dynamics of doped CoFeB trilayers and a comparison to the quasistatic approximation

Forrester, Derek Michael; Kusmartsev, F. V.; Kovács, Endre

doi:10.1103/physrevb.87.174416

Cited by 5 publications

(17 citation statements)

References 57 publications

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“…Again, to reiterate the findings of the two nanomagnet systems [15] before increasing N we now state the limits of the AF 2 phase to be,…”

Section: Resultsmentioning

confidence: 68%

“…A resulting dimensionless form is found by dividing by M s 2 and writing time as t = τ/γ M s . The dimensionless parameters used here ( J , e , a , b , and h x , y , z ), have also been divided by N x throughout [15]. The magnetizations are defined through ∂ φ i / ∂ τ and ∂ θ i / ∂ τ.…”

Section: Resultsmentioning

confidence: 99%

“…2 has four coupled nanomagnets each of dimensions l x = 186 nm, l y = 20 nm, and l z = 1.5 nm (with N x = 0.00454 and N z = 0.88269). With the inclusion of a thermally induced fluctuation, λ (see [15]) the number of plateaus can be variable. The small perturbation to the system can result in metastability and the magnetic field should be cycled many times in order to obtain all possible Barkhausen jumps, in accordance with the energy balances of the system under investigation.…”

Section: Resultsmentioning

confidence: 99%

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Designing magnetic superlattices that are composed of single domain nanomagnets

Forrester¹,

Kusmartsev²,

Kovács³

2014

Beilstein J. Nanotechnol.

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Summary Background: The complex nature of the magnetic interactions between any number of nanosized elements of a magnetic superlattice can be described by the generic behavior that is presented here. The hysteresis characteristics of interacting elliptical nanomagnets are described by a quasi-static method that identifies the critical boundaries between magnetic phases. A full dynamical analysis is conducted in complement to this and the deviations from the quasi-static analysis are highlighted. Each phase is defined by the configuration of the magnetic moments of the chain of single domain nanomagnets and correspondingly the existence of parallel, anti-parallel and canting average magnetization states. Results: We give examples of the phase diagrams in terms of anisotropy and coupling strength for two, three and four magnetic layers. Each phase diagrams character is defined by the shape of the magnetic hysteresis profile for a system in an applied magnetic field. We present the analytical solutions that enable one to define the “phase” boundaries between the emergence of spin-flop, anti-parallel and parallel configurations. The shape of the hysteresis profile is a function of the coupling strength between the nanomagnets and examples are given of how it dictates a systems magnetic response. Many different paths between metastable states can exist and this can lead to instabilities and fluctuations in the magnetization. Conclusion: With these phase diagrams one can find the most stable magnetic configurations against perturbations so as to create magnetic devices. On the other hand, one may require a magnetic system that can easily be switched between phases, and so one can use the information herein to design superlattices of the required shape and character by choosing parameters close to the phase boundaries. This work will be useful when designing future spintronic devices, especially those manipulating the properties of CoFeB compounds.

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“…Again, to reiterate the findings of the two nanomagnet systems [15] before increasing N we now state the limits of the AF 2 phase to be,…”

Section: Resultsmentioning

confidence: 68%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Designing magnetic superlattices that are composed of single domain nanomagnets

Forrester¹,

Kusmartsev²,

Kovács³

2014

Beilstein J. Nanotechnol.

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“…As this is a dynamical study, we also include an indication of the switching times of the magnetic moments of the structures (see Ref. for a detailed analysis of switching in two magnetic layer systems). In Fig.…”

Section: Synthetic Antiferromagnetic Nanoparticlesmentioning

confidence: 99%

“…Figure shows the hysteresis profile with a typical spin‐flop (e.g., ) appearance for an independent SAF structure. Here, we deliberately sought to give an example whereby there are clear hysteresis losses.…”

Section: Synthetic Antiferromagnetic Nanoparticlesmentioning

confidence: 99%

The nano‐mechanics and magnetic properties of high moment synthetic antiferromagnetic particles

Forrester

Kusmartsev

2014

Physica Status Solidi (a)

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Phone: þ44 (0) 1509 228208With nanomagnets increasingly being used and proposed as functional units for in vivo applications, it is vital to understand how to optimize their structure, geometry, and size, and their responses to electromagnetic stimulation. Herein, we predicate how to do so for synthetic antiferromagnetic structures that are subjected to external magnetic control. Because the structures are on the scale of biological entities, interactions with cells and molecular constituents can be extreme and careful design must be undertaken to avoid detrimental effects. Thus, the magnetic responses of multilayers, as demonstrated in experiments by Koh et al. [e.g., Hu et al., Adv. Mater. 20, 1479 and Koh et al., J. Appl. Phys. 107, 09B522 (2010)], are understood using a fully dynamical investigation based on LandauLifshitz-Gilbert equations. We find that during the fabrication of the structures the axial positions of the nanomagnets become offset from each other, leading to the characteristic magnetic hysteresis shapes witnessed. We then find the magnetic nanomechanical forces generated by such structures.The conical synthetic antiferromagnetic nanoparticles with two magnetic layers -Left: the magnetic flux density is shown on the surface of the structure in a magnetic flux density of B ¼ 0.08 T. Middle and right: orientations of the magnetic moments of the two magnetic layers.

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The absorption of ultrasound in emulsions: computational modelling of thermal effects

Forrester

Pinfield

2018

Sci Rep

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Around liquid particles in a fluid of contrasting properties (for example, oil in water) in ultrasonic fields there are small regions where thermal waves can propagate with relatively high amplitudes. Herein, we demonstrate the existence and character of these waveforms using three-dimensional finite element modelling based on linearised Navier-Stokes equations. We investigate single particles and small clusters of particles, validating the expected thermal wavelength and the power dissipation due to viscous and thermal effects around the particle. The energy lost due to thermal and viscous dissipation is explored as a function of the average separation distance between the particles (linking to concentration) as well as the applied frequency. The determination of energy loss provides a new method for calculating the attenuation in particle systems. We demonstrate that the effective attenuation of an emulsion in which particles exist in clusters is influenced by the interparticle separation within the cluster, even at the same total particle concentration. Thus, the finite element modelling provides evidence for thermal interactions and their effect in correlated particle systems.

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Switching dynamics of doped CoFeB trilayers and a comparison to the quasistatic approximation

Cited by 5 publications

References 57 publications

Designing magnetic superlattices that are composed of single domain nanomagnets

Designing magnetic superlattices that are composed of single domain nanomagnets

The nano‐mechanics and magnetic properties of high moment synthetic antiferromagnetic particles

The absorption of ultrasound in emulsions: computational modelling of thermal effects

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