Single domain

About: Single domain is a research topic. Over the lifetime, 5399 publications have been published within this topic receiving 122355 citations.

Spin Dynamics in Confined Magnetic Structures III

Abstract: Fast Switching of Mesoscopic Magnets.- Spin Damping in Ultrathin Magnetic Films.- Magnetization Dynamics Investigated by Time-Resolved Kerr Effect Magnetometry.- High Speed Switching and Rotational Dynamics in Small Magnetic Thin Film Devices.- Time-Resolved X-Ray Magnetic Circular Dichroism - A Selective Probe of Magnetization Dynamics on Nanosecond Timescales.- The Dynamic Response of Magnetization to Hot Spins.- Ultrafast Magnetization and Switching Dynamics.- Laser-Induced Magnetization Dynamics.

Particle Size Dependence of Coercivity and Remanence of Single‐Domain Particles

Abstract: The coercive force and remanence of essentially spherical iron and iron‐cobalt alloy particles with diameters from 20 to 3000 A have been measured at 4°, 76°, and 207°K and compared to the theoretically predicted behavior. The remanence shows a broad, plateau‐like maximum while the coercive force has a rather sharp maximum. The maximum of the coercive force occurs at a much larger particle diameter than the maximum of the remanence. It is shown that these essential characteristics follow from the theory. Deviations from theory are seen in the smaller size range and can be accounted for by the distribution of particle sizes. A general treatment of the coercive force of mixtures of thermally stable, high coercive force particles with superparamagnetic and multidomain particles is given.

Wasp-waisted hysteresis loops: Mineral magnetic characteristics and discrimination of components in mixed magnetic systems

Abstract: Rock magnetic studies of complex systems that contain mixtures of magnetic minerals or mixed grain size distributions have demonstrated the need for a better method of distinguishing between different magnetic components in geological materials. Hysteresis loops that are constricted in the middle section, but are wider above and below the middle section, are commonly observed in mixed magnetic assemblages. Such “wasp-waisted” hysteresis loops have been widely documented, particularly with respect to rare earth permanent magnets, basaltic lava flows, remagnetized Paleozoic carbonate rocks, and an increasingly wide range of other rocks. Our modelling, combined with a review of previous work, indicates that there are several conditions that give rise to, as well as magnetic properties that are characteristic of, wasp-waisted hysteresis loops. First, at least two magnetic components with strongly contrasting coercivities must coexist. This condition can arise from either mixtures of grain sizes of a single magnetic mineral, or a combination of magnetic minerals with contrasting cocrcivities, or a combination of these two situations. Second, materials that give rise to wasp-waisted hysteresis loops will have relatively high ratios of the coercivity of remanence to coercive force (B cr /B c ) because B0 is controlled by the soft (low coercivity) component, whereas Bcris controlled by the hard (high coercivity) component. Third, values of B cr /B c ? 10 usually only occur for strongly wasp-waisted loops when the low coercivity component comprises an overwhelmingly large fraction of the total volume of magnetic grains. Fourth, a given mixture of superparamagnetic and single-domain (SD) grains is more likely to give rise to wasp-waisted hysteresis loops than an equivalent mixture of SD and multidomain grains. Fifth, our results provide empirical confirmation that the total magnetization of a material is the sum of the weighted contributions of each component, in the absence of significant magnetic interaction between particles. Thus to contribute significantly to wasp-waisted behavior, a mineral magnetic component must give rise to a significant portion of the total magnetization of the rock. As a result, minerals with weak magnetic moments such as hematite need to occur in large concentrations to cause wasp-waistedness in materials that also contain ferrimagnetic minerals. We outline a method for determining the magnetic components that can give rise to wasp-waisted hysteresis loops. This method is based on high- and low-temperature magnetic measurements that are used to identify the dominant remanence-bearing mineral/s and on mineral magnetic techniques that are used to discriminate between different magnetic domain states. The method is illustrated with several examples from archaeological, geological, and synthetic materials.

Hexagonally ordered 100 nm period nickel nanowire arrays

Abstract: The magnetic behavior of 100 nm period arrays of Ni nanowires embedded in a highly ordered alumina pore matrix were characterized by magnetometry and magnetic force microscopy. Reducing the diameter of the nanowires from 55 to 30 nm while keeping the interwire distance constant leads to increasing coercive fields from 600 to 1200 Oe and to increasing remanence from 30% to 100%. The domain structure of the arrays exhibits in the demagnetized state a labyrith-like pattern. These results show that stray field interactions of single domain nanowires are entirely dependent on the nanowire diameter.

Experimental Evidence of the Néel-Brown Model of Magnetization Reversal

Abstract: Presented are the first magnetization measurements of individual ferromagnetic nanoparticles (15--30 nm) at very low temperatures (0.1--6 K). The angular dependence of the hysteresis loop evidenced the single domain character of the particles. Waiting time, switching field, and telegraph noise measurements showed for the first time that the magnetization reversal of a well prepared ferromagnetic nanoparticle can be described by thermal activation over a single-energy barrier as originally proposed by N\'eel and Brown. The ``activation volume'' estimated by these measurements was close to the particle volume.