Magnetic properties of Ni nanowires electrodeposited into self-assembled porous alumina arrays have been investigated. By anodizing aluminum in sulfuric acid and immersing the as-anodized template into phosphoric acid for different lengths of time, we are able to vary the diameters of the subsequently deposited nanowires between 8 and 25 nm. The coercivity measured along wire axis first increases with the wire diameter, reaches a maximum of 950 Oe near a diameter of 18 nm, and then decreases with further increase of wire diameter. The dependence of the magnetization of Ni nanowires is found to follow Bloch's law at low temperature but with the Bloch exponent decreasing from the bulk value and the Bloch constant increasing from the bulk value by an order of magnitude.

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We present experimental results on magnetization reversal for a class of nanoscale magnetic films with perpendicular magnetic anisotropy and develop a model that describes a variety of related experiments.In this Inodel the sample is divided into identical single domain cells that interact through dipolar fields and a nearest-neighbor domain-wa11 interaction. Monte Carlo simulations give insights into the relationship between the macroscopic magnetic parameters and the reversal behavior and demonstrate the important role that thermal activation plays in the reversal process.Among the most exciting advances in modern condensed-matter and materials physics is the incipient development of an ability to understand and design structures with nanometer-length scales. ' These structures and the technologies based on them will be important in areas such as information storage, electronic devices, and biotechnology.As the dimensions of the fundamental building blocks or cells of magnetization, polarization, etc. , become smaller and smaller, the temporal stability of an ordered phase within the ce11 becomes of crucial importance. This problem is also intimately connected to the mechanism by which a reversal or switch of the order parameter in the cell occurs as the result of an applied stimulus.This paper is concerned with time decay and reversal phenomena in an important class of nanostructured thin films, amorphous magnetic multilayers with characteristic layer thicknesses of a few atomic diameters. Such films have considerable potential in future ultra-highdensity magneto-optic data storage systems. Magnetization reversal has been studied in a number of nanostructured thin-film and amorphous rareearth -transition-metal systems. ' These earlier measurements explicitly show that the reversal behavior in these systems tends to fall between one of two limiting categories: (a) continuous nucleation with the magnetization varying approximately as ln(t) for a significant period of time, and (b) slow nucleation followed by rapid domain growth.These two limiting behaviors are illustrated in Fig. 1 for Dy/Fe compositionally modulated multilayer samples, where the polar Kerr angle 0&, which is proportional to the magnetization M, is plotted as a function of time. " These measurements were carried out by first saturating the sample with a large magnetic field perpendicular to the film and then reversing the field to a value near the coercive field H, (the applied field for which M=0) and holding it constant while the Kerr rotation was monitored. The dashed line shows the time dependence of the polar Kerr rotation of a Dy(5 A)/Fe(8. 1 A) sample, which illustrates type-(a) behavior. The Kerr rotation completely reverses only for applied fields greater than the saturation field (the applied field for which Otf irst reaches its maximum value), and at longer times the 0.2 0.1 0.0 -0.1 -0.2 2PP 400 600 Time (s} 800 FIG. 1. Measured Kerr rotation angle as a function of time after field reversal for Dy(5 A)/Fe(5. 6 A) (solid line) an...

Background and Purpose Inhibition of the G‐protein gated ACh‐activated inward rectifier potassium current, IK,ACh may be an effective atrial selective treatment strategy for atrial fibrillation (AF). Therefore, the anti‐arrhythmic and electrophysiological properties of a novel putatively potent and highly specific IK,ACh inhibitor, XAF‐1407 (3‐methyl‐1‐[5‐phenyl‐4‐[4‐(2‐pyrrolidin‐1‐ylethoxymethyl)‐1‐piperidyl]thieno[2,3‐d]pyrimidin‐6‐yl]azetidin‐3‐ol), were characterised for the first time in vitro and investigated in horses with persistent AF. Experimental Approach The pharmacological ion channel profile of XAF‐1407 was investigated using cell lines expressing relevant ion channels. In addition, eleven horses were implanted with implantable cardioverter defibrillators enabling atrial tachypacing into self‐sustained AF. The electrophysiological effects of XAF‐1407 were investigated after serial cardioversions over a period of 1 month. Cardioversion success, drug‐induced changes of atrial tissue refractoriness, and ventricular electrophysiology were assessed at baseline (day 0) and days 3, 5, 11, 17, and 29 after AF induction. Key Results XAF‐1407 potently and selectively inhibited Kir3.1/3.4 and Kir3.4/3.4, underlying the IK,ACh current. XAF‐1407 treatment in horses prolonged atrial effective refractory period as well as decreased atrial fibrillatory rate significantly (~20%) and successfully cardioverted AF, although with a decreasing efficacy over time. XAF‐1407 shortened atrioventricular‐nodal refractoriness, without effect on QRS duration. QTc prolongation (4%) within 15 min of drug infusion was observed, however, without any evidence of ventricular arrhythmia. Conclusion and Implications XAF‐1407 efficiently cardioverted sustained tachypacing‐induced AF of short duration in horses without notable side effects. This supports IK,ACh inhibition as a potentially safe treatment of paroxysmal AF in horses, suggesting potential clinical value for other species including humans.

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