Magnetic hysteresis and minor loops: models and experiments

Barker, John A.; Schreiber, Donald E.; Huth, B. G.; Everett, D. H.

doi:10.1098/rspa.1983.0035

Cited by 79 publications

(30 citation statements)

References 15 publications

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“…Common examples are mechanical marking or the flipping of magnetic domains. More exotic examples include return-point memory [1,2] and aging and rejuvenation in glasses [3,4]. These systems all support the intuition that (i) the more times an input is presented the stronger the memory becomes, and (ii) random noise is detrimental to memory retention.…”

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confidence: 64%

“…Keim and Nagel [7] described how multiple transient memories could occur in a simplified model of a suspension under cyclic shear: When sheared repeatedly between strain amplitudes γ = 0 and γ = γ 1 , a suspension can organize into a reversible steady state, thereby encoding a memory of γ 1 . The memory appears as a sudden drop in reversibility as the strain amplitude is swept past γ 1 .…”

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confidence: 99%

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Multiple Transient Memories in Experiments on Sheared Non-Brownian Suspensions

2014

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A system with multiple transient memories can remember a set of inputs but subsequently forgets almost all of them, even as they are continually applied. If noise is added, the system can store all memories indefinitely. The phenomenon has recently been predicted for cyclically sheared nonBrownian suspensions. Here we present experiments on such suspensions, finding behavior consistent with multiple transient memories and showing how memories can be stabilized by noise.PACS numbers: 05.65.+b, 82.70.Kj A physical system has memory if it is endowed with the basic operations of imprinting, retrieval, and erasure. Common examples are mechanical marking or the flipping of magnetic domains. More exotic examples include return-point memory [1,2] and aging and rejuvenation in glasses [3,4]. These systems all support the intuition that (i) the more times an input is presented the stronger the memory becomes, and (ii) random noise is detrimental to memory retention. However, both attributes are violated by multiple transient memories, which have been seen in traveling charge-density waves [5,6] and predicted for sheared non-Brownian suspensions [7,8]. The experiments reported here on sheared suspensions demonstrate that noise can stabilize this form of memory retention.Keim and Nagel [7] described how multiple transient memories could occur in a simplified model of a suspension under cyclic shear: When sheared repeatedly between strain amplitudes γ = 0 and γ = γ 1 , a suspension can organize into a reversible steady state, thereby encoding a memory of γ 1 . The memory appears as a sudden drop in reversibility as the strain amplitude is swept past γ 1 . Multiple memories can be formed if several amplitudes, γ 1 < γ 2 < ... < γ n , are repeatedly applied. However, once the suspension relaxes to a state that is completely reversible up to amplitude γ n , it is also reversible for all γ < γ n ; thus the memories of all the smaller training amplitudes are effectively erased. The presence of noise was predicted to prevent the system from reaching a fully reversible state so that other memories could be retained.For multiple transient memories in charge-density waves, the role of noise was only demonstrated in a simulation [6]; in experiments [5] the ambient noise could not be varied and was assumed to be strong enough so that the system could remember all inputs. In the present paper, we cyclically shear neutrally buoyant, non-Brownian suspensions at low Reynolds number. By varying the noise, we demonstrate explicitly that noise is required to retain a memory of all input strain amplitudes at long times. This provides a concrete example of the emergence of plasticity in memory.Experiment.-In the experiment, a viscous suspension is cyclically sheared in a 6.3 mm gap between two cylinders in a circular Couette geometry (with an inner cylinder radius of 36.6 mm). The suspension is composed of PMMA spheres (Cospheric, LLC) in a mixture of Triton X-100, water, and zinc chloride (dynamic viscosity µ = 4,300 mPa s) that is index a...

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Multiple Transient Memories in Experiments on Sheared Non-Brownian Suspensions

2014

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“…We believe that in order for multicycles to be seen, it is essential for the interaction between pillars to be sufficiently strong to cause avalanches; in the extreme case, when the pillars are independent, it is clear that a one-cycle hysteresis loop would be seen. However, avalanches are not sufficient to produce disorder: for disordered nearest neighbor Ising ferromagnets, the phenomenon of Return Point Memory [11,12] (RPM) can be proved, precluding multicycles. This emphasizes the need for frustration.…”

Section: Introductionmentioning

confidence: 99%

Hysteresis multicycles in nanomagnet arrays

Mai¹,

Narayan²

2005

Phys. Rev. E

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We predict two new physical effects in arrays of single-domain nanomagnets by performing simulations using a realistic model Hamiltonian and physical parameters. First, we find hysteretic multicycles for such nanomagnets. The simulation uses continuous spin dynamics through the Landau-Lifshitz-Gilbert (LLG) equation. In some regions of parameter space, the probability of finding a multicycle is as high as ∼ 0.6. We find that systems with larger and more anisotropic nanomagnets tend to display more multicycles. Our results also demonstrate the importance of disorder and frustration for multicycle behavior. Second, we show that there is a fundamental difference between the more realistic vector LLG equation and scalar models of hysteresis, such as Ising models. In the latter case spin and external field inversion symmetry is obeyed, but in the former it is destroyed by the dynamics, with important experimental implications.

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“…To study the elastic and plastic response of the column, we utilize an incremental stresscycling protocol; which is the mechanical equivalent of minor hysteresis loop in magnets [44]. Here, the column is recursively stressed such that the minor loops have three branches: (i) an increase−ϑ branch where the tilt angle increases from 0 to ϑ m n at a fixed rate (ii) a clamp−ϑ branch where the tilt angle is held constant at ϑ m n for a fixed period of clamping time and (iii) a decrease−ϑ branch which corresponds to decreasing the tilt angle from ϑ m n to 0, with the same rate as in (i).…”

Section: An Order Of Magnitude Estimate Of the Elastic Constantmentioning

confidence: 99%

Mechanics of a granular skin

et al. 2017

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Magic Sand, a hydrophobic toy granular material, is widely used in popular science instructions because of its non-intuitive mechanical properties. A detailed study of the failure of an underwater column of magic sand shows that these properties can be traced to a single phenomenon: the system self-generates a cohesive skin that encapsulates the material inside. The skin, consists of pinned air-water-grain interfaces, shows multi-scale mechanical properties: they range from contactline dynamics in the intra-grain roughness scale, plastic flow at the grain scale, all the way to the sample-scale mechanical responses. With decreasing rigidity of the skin, the failure mode transforms from brittle to ductile (both of which are collective in nature) to a complete disintegration at the single grain scale.

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Magnetic hysteresis and minor loops: models and experiments

Cited by 79 publications

References 15 publications

Multiple Transient Memories in Experiments on Sheared Non-Brownian Suspensions

Multiple Transient Memories in Experiments on Sheared Non-Brownian Suspensions

Hysteresis multicycles in nanomagnet arrays

Mechanics of a granular skin

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