Disorder-induced magnetic memory: Experiments and theories

Pierce, Michael S.; Buechler, C. R.; Sorensen, L. B.; Kevan, S. D.; Jagla, E. A.; Deutsch, J. M.; Mai, Trieu; Narayan, Onuttom; Davies, Joseph E.; Liu, Kai; Zimányi, Gergely T.; Katzgraber, Helmut G.; Hellwig, Olav; Fullerton, Eric E.; Fischer, Peter; Kortright, J. B.

doi:10.1103/physrevb.75.144406

Cited by 69 publications

(82 citation statements)

References 47 publications

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“…Controlling field history leads to formation of complex domain morphologies, associated with violation of microscopic return point memory 14,15 . These studies potentially enable new generation of computational and data storage devices.…”

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confidence: 99%

Ionic field effect and memristive phenomena in single-point ferroelectric domain switching

et al. 2014

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Electric field-induced polarization switching underpins most functional applications of ferroelectric materials in information technology, materials science and optoelectronics. Recently, much attention has been focused on the switching of individual domains using scanning probe microscopy. The classical picture of tip-induced switching, including formation of cylindrical domains with size, is largely determined by the field distribution and domain wall motion kinetics. The polarization screening is recognized as a necessary precondition to the stability of ferroelectric phase; however, screening processes are generally considered to be uniformly efficient and not leading to changes in switching behaviour. Here we demonstrate that single-point tip-induced polarization switching can give rise to a surprisingly broad range of domain morphologies, including radial and angular instabilities. These behaviours are traced to the surface screening charge dynamics, which in some cases can even give rise to anomalous switching against the electric field (ionic field effect).

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confidence: 99%

Ionic field effect and memristive phenomena in single-point ferroelectric domain switching

et al. 2014

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“…Many studies were devoted to the macroscopic and microscopic repeatability of minor and major hysteresis loops and effects of disorder on cycle-to-cycle memory [1,2]. Macroscopically the major loops repeat themselves in successive cycles, however it was appreciated [3,4] that disorder induces memory in the microscopic magnetic domain configurations from one cycle of the hysteresis loop to the next, even when H sat was crossed. Successive minor loops are usually reasonably reproducible, although changes of size and shape were observed [5][6][7].…”

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confidence: 99%

Dynamics of successive minor hysteresis loops

2012

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Cumulative growth of successive minor hysteresis loops in Co/Pd multilayers with perpendicular anisotropy was studied in the context of time dependent magnetization reversal dynamics. We show that in disordered ferromagnets, where magnetization reversal involves nucleation, domains' expansion and annihilation, differences between the time dependencies of these processes are responsible for accumulation of nuclei for rapid domain expansion, for the asymmetry of forward and backward magnetization reversals and for the respective cumulative growth of hysteresis loops. Loops stop changing and become macroscopically reproducible when populations of upward and downward nucleation domains balance each other and the respective upward and downward reversal times stabilize. PACS: 75.60.Jk, 75.70.Cn, IntroductionReproducibility of cycling processes under identical external conditions attracts particular attention in studies of magnetic hysteresis for at least two reasons: the effect is fundamental to all magnetic storage technologies, and it can serve as a model for a wide range of type-I phase transitions. Two types of hysteresis loops are distinguished."Major" loops are obtained by sweeping the applied field beyond the saturation field H sat , above which the system is said to be fully saturated and its magnetization M(H) is a single-valued function of the applied field H; "minor" loops are obtained when the cycle is limited to fields near and below H sat . Many studies were devoted to the macroscopic and microscopic repeatability of minor and major hysteresis loops and effects of disorder on cycle-to-cycle memory [1,2]. Macroscopically the major loops repeat themselves in successive cycles, however it was appreciated [3,4] that disorder induces memory in the microscopic magnetic domain configurations from one cycle of the hysteresis loop to the next, even when H sat was crossed. Successive minor loops are usually reasonably reproducible, although changes of size and shape were observed [5][6][7]. Nevertheless these finite perturbations did not undermine a generally accepted view that macroscopic hysteresis loops are repeatable. It came therefore as a surprise when Berger et al. [8] reported major cumulative expansion of successive minor hysteresis loops in Co/Pt and Co/Pd multilayers even up to four times their initial area. The phenomenon was explained in terms of successive accumulation of small nucleation domains, i.e. microscopic areas of reversed magnetization that act as nuclei for the subsequent macroscopic magnetization reversal [8,9]. The reversals at all but the first cycle do not start anew from a fully saturated state but from a preconfigured state in which nuclei for domain expansion are locally conserved. Conservation and accumulation of the nuclei can happen if the system responds asymmetrically in forward and reverse field orientations such that small domains appear to be substantially more stable toward annihilation in an opposite field than toward expansion in a forward field.In this paper we shall de...

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“…Finally in the 20nm sized dots, the FORC distribution is much broader (Fig. 3c) due to a relatively higher degree of disorders [24,34]. We also observed an abnormal drop in coercivity for the 20 nm sized sample.…”

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confidence: 51%