Switching field studies of individual single domain Ni columns

O’Barr, R.; Schultz, S.

doi:10.1063/1.364569

Cited by 57 publications

(15 citation statements)

References 17 publications

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“…Previous experiments were performed, in general, on large assemblies of theoretically identical particles, even if the real dispersion of the sample in terms of size, morphology, composition, orientation and separation between the different magnetic entities was clearly hiding several factors and limiting the interpretation of the results. Nowadays, electron holography [466], micro-SQUID (Superconducting Quantum Interference Device) [467] and Magnetic Force Microscopy techniques [468,469] have made possible the study of magnetization switching in single nanowires.…”

Section: Magnetization Reversal Studies In 1d Metallic Nanostructuresmentioning

confidence: 99%

Physical properties of elongated inorganic nanoparticles

et al. 2011

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Section: Magnetization Reversal Studies In 1d Metallic Nanostructuresmentioning

confidence: 99%

Physical properties of elongated inorganic nanoparticles

et al. 2011

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“…To achieve this, we combine standard bulk magnetization measurements ͓using superconducting quantum interference device ͑SQUID͒ magnetometry͔ with microscopic techniques such as atomic and magnetic force microscopy ͑AFM/MFM͒. Recent reports by other groups 15,[17][18][19][20] have shown such an approach to be very fruitful indeed. When compared to these studies, the nanowires prepared in alumite membranes are ideal systems for investigating the sole effect of interactions, i.e., separated from other effects such as thermal relaxation or inhomogeneous remanent states.…”

Section: Introductionmentioning

confidence: 99%

Magnetization reversal of ferromagnetic nanowires studied by magnetic force microscopy

et al. 2003

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The magnetization reversal of two-dimensional arrays of parallel ferromagnetic Fe nanowires embedded in nanoporous alumina templates has been studied. By combining bulk magnetization measurements ͑supercon-ducting quantum interference device magnetometry͒ with field-dependent magnetic force microscopy ͑MFM͒, we have been able to decompose the macroscopic hysteresis loop in terms of the irreversible magnetic responses of individual nanowires. The latter are found to behave as monodomain ferromagnetic needles, with hysteresis loops displaced ͑asymmetric͒ as a consequence of the strong dipolar interactions between them. The application of field-dependent MFM provides a microscopic method to obtain the hysteresis curve of the array, by simply registering the fraction of up and down magnetized wires as a function of applied field. The observed deviations from the rectangular shape of the macroscopic hysteresis loop of the array can be ascribed to the spatial variation of the dipolar field through the inhomogeneously filled membrane. The system studied proves to be an excellent example of the two-dimensional classical Preisach model, well known from the field of hysteresis modeling and micromagnetism.

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“…In our case, the curling mode prediction for a prolate spheroid [29] (assuming an exchange length d ex = 40 nm and bulk saturation magnetization M S = 0.485 T; the demagnetization factors along the major and minor axes are D z = 0.00015 and D x = 0.5, respectively) gives H sw = 140 Oe at θ = 0. The underestimation of H sw value at θ = 0 has been reported for nanowires with d/d ex > 3 [30]. The curling model overestimates H sw at θ = 80…”

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confidence: 92%

Field-tunable stochasticity in the magnetization reversal of a cylindrical nanomagnet

2010

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The nature of magnetization reversal in an isolated cylindrical nanomagnet has been studied employing time-resolved magnetoresistance measurement. We find that the reversal mode is highly stochastic, occurring either by multimode or single-step switching. Intriguingly, the stochasticity was found to depend on the alignment of the driving magnetic field to the long axis of the nanowires, where predominantly multimode switching gives way to single-step switching behavior as the field direction is rotated from parallel to transverse with respect to the nanowire axis.Traditionally, cylindrical nanomagnets have been of great interest for high density magnetic storage [1], but very recently the dynamics of domain walls (DW) in these systems is also rapidly gaining in importance. A driving factor to this is the absence of "Walker breakdown", with the DWs acting as "massless" particles having zero kinetic energy [2]. However, a generic problem, in both planar or cylindrical nanowires, is the stochasticity associated with the magnetization reversal process. This is manifested in two classes of phenomena: first, the stochasticity associated with diffusive and nondeterministic motion of the DWs in presence of artificial or intrinsic disorder (addressed elsewhere by the same authors [3]); second, the stochasticity related to the nucleation and subsequent propagation of DWs. The latter has been investigated in several planar magnetic films and lithographically patterned nanowires through, for example, size and shape distributions of Barkhausen avalanches, or extraordinary Hall effect etc [4]. Asymmetry in the mode of magnetization switching process on reversal of magnetic field polarity has been investigated using magnetic force microscopy [5], which might as well be related to the stochasticity issue (MFM probes only a fraction of the whole sample). The stochasticity in magnetization reversal in case of cylindrical nanowires, however, is relatively unexplored.Cylindrical magnets have been the classical template for theoretical study of the mode of magnetization reversal and more importantly the angular variation of the nucleation field, albeit in the limit of an infinite and isotropic cylinder [6]. Many experiments on magnetization reversal in nanoscale magnetic systems have looked at the angular dependence assuming an infinite and isotropic cylinder (or strips), although finite size and anisotropy related effects can be crucial in those cases [7][8][9][10][11][12][13][14][15]. Wegrowe et al. could fit their data on angular dependence with the curling mode prediction for an infinite cylinder assuming an activation volume with aspect ratio 2 : 1 (Ref. [16]). Moreover, surface anisotropy or structural defects can also play crucial role and hence cannot be treated within the framework of isotropic magnetization [16]. The principal objective of this article is to explore the effect of angular variation on the stochasticity of magnetization reversal, rather than the variation in switching field (H sw ), where we show that finite...

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Switching field studies of individual single domain Ni columns

Cited by 57 publications

References 17 publications

Physical properties of elongated inorganic nanoparticles

Physical properties of elongated inorganic nanoparticles

Magnetization reversal of ferromagnetic nanowires studied by magnetic force microscopy

Field-tunable stochasticity in the magnetization reversal of a cylindrical nanomagnet

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