Reconfigurable Training, Vortex Writing and Spin-Wave Fingerprinting in an Artificial Spin-Vortex Ice

Abstract Strongly-interacting artificial spin systems are moving beyond mimicking naturally-occurring materials to find roles as versatile functional platforms, from reconfigurable magnonics to designer magnetic metamaterials. Typically artificial spin systems comprise nanomagnets with a single magnetisation texture: collinear macrospins or chiral vortices. By tuning nanoarray dimensions we achieve macrospin/vortex bistability and demonstrate a four-state metamaterial spin-system ‘Artificial Spin-Vortex Ice’ (ASVI). ASVI is capable of adopting Ising-like macrospins with strong ice-like vertex interactions, in addition to weakly-coupled vortices with low stray dipolar-field. The enhanced bi-texture microstate space gives rise to emergent physical memory phenomena, with ratchet-like vortex training and history-dependent nonlinear training dynamics. We observe vortex-domain formation alongside MFM tip vortex-writing. Tip-written vortices dramatically alter local reversal and memory dynamics. Vortices and macrospins exhibit starkly-differing spin-wave spectra with analogue-style mode-amplitude control via vortex training and mode-frequency shifts of ∆f = 3.8 GHz. We leverage spin-wave ‘spectral fingerprinting’ for rapid, scaleable readout of vortex and macrospin populations over complex training-protocols with applicability for functional magnonics and physical memory.

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Visualization of domain formation in the inner and outer leaflets of a phospholipid bilayer.

The Journal of Cell Biology ◽

10.1083/jcb.106.6.1885 ◽

1988 ◽

Vol 106 (6) ◽

pp. 1885-1892 ◽

Cited By ~ 28

Author(s):

D M Haverstick ◽

M Glaser

Keyword(s):

Phosphatidic Acid ◽

Digital Image ◽

Acyl Chain ◽

Fluorescence Microscope ◽

Phospholipid Bilayer ◽

Domain Formation ◽

Charge Coupled Device ◽

Image Processor ◽

Outer Leaflet ◽

Naturally Occurring

Large vesicles (5-10-micron in diameter) were formed in the presence of phospholipids fluorescently labeled on the acyl chain and visualized using a fluorescence microscope, charge-coupled-device camera and digital image processor. When such vesicles contained a fluorescent phosphatidic acid (PA) and were exposed to 2 mM CaCl2 or 0.5 mM PrCl3, it was possible to visualize PA-enriched domains within the vesicles. Calcium-induced domain formation was reversible in the presence of 4 mM EGTA. Vesicles were formed containing fluorescent PA on either the inner or outer leaflet of the bilayer and the patching and dissolution of patching were studied under conditions where calcium was present on the outside of the vesicle and where calcium was distributed across the bilayer. In addition, vesicles were formed with two different fluorescent PA's, one on the inner leaflet and a different one on the outer leaflet of the bilayer. The results of the experiments show that in vesicles formed primarily with naturally occurring phospholipids such as egg phosphatidylcholine or brain phosphatidylethanolamine, there was no coordinate action of the two leaflets of the bilayer. An exception to this was found, however, if the vesicles were formed in the presence of primarily dioleoyl phospholipids (greater than 95 mol %). In these vesicles there was a coordinate or coupled response to calcium by the two leaflets of the bilayer. In most cases, however, the two leaflets of the bilayer showed independent or uncoupled domain formation.

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Origin of Temperature Gradient in Nonequilibrium Steady States in Weakly Coupled Quantum Spin Systems

Journal of the Physical Society of Japan ◽

10.7566/jpsj.85.074006 ◽

2016 ◽

Vol 85 (7) ◽

pp. 074006

Author(s):

Toyohiko Ishida ◽

Ayumu Sugita

Keyword(s):

Temperature Gradient ◽

Quantum Spin ◽

Steady States ◽

Spin Systems ◽

Nonequilibrium Steady States ◽

Quantum Spin Systems ◽

Weakly Coupled

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Why is the Tc So High in Fe-Based Pnictide and Chalcogenide Superconductors?

MRS Proceedings ◽

10.1557/opl.2014.880 ◽

2014 ◽

Vol 1684 ◽

Cited By ~ 3

Author(s):

Bing Lv ◽

Liangzi Deng ◽

Zheng Wu ◽

Fengyan Wei ◽

Kui Zhao ◽

...

Keyword(s):

Single Crystals ◽

Magnetic Measurements ◽

Collective Excitations ◽

Weak Links ◽

Meissner State ◽

Bulk Superconductivity ◽

Naturally Occurring ◽

Weakly Coupled ◽

Temperature Ranges ◽

Frequency Dependences

ABSTRACTRecently, the detection of non-bulk superconductivity with unexpectedly high onset-Tcs up to 49 K in Pr-doped CaFe2As2 [(Ca,Pr)122] single crystals and the report of a Tc up to 65 K in one-unit-cell (1UC) FeSe epi-films, offer an unusual opportunity to seek an answer to the question posed in the title. Through systematic compositional, structural, resistive, and magnetic investigations on (Ca,Pr)122 single crystals, we have observed a doping-level-independent Tc, the simultaneous appearance of superparamagnetism and superconductivity, large magnetic anisotropy, and the existence of mesoscopic-2D structures in these crystals, thus providing clear evidence consistent with the proposed interface-enhanced Tc in these naturally occurring rareearth-doped Fe-based superconductors, (Ca,R)122. Similar resistive and magnetic measurements were also made on the 3–4UC FeSe ultrathin epi-films. We have detected weak links in the Meissner state below 20 K, weakly coupled small superconducting patches between 20–45 K, and collective excitations of spin and/or superconducting nature between 45–80 K. The unusual frequency dependences of the diamagnetic moment observed in the films in different temperature ranges will be presented and their implications discussed.

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