The materials used in magnetic recording heads have recently received a tremendous amount of attention. This has been the result of a fortunate set of circumstances. Ever-increasing demands for information storage, especially for graphics-intensive applications, have necessitated unprecedented increases in disk-drive areal densities. Combined with this are recent discoveries in the area of magnetoresistive materials, enabling the design and fabrication of much more sensitive recording heads. The end result is a flurry of activity that has come to dominate the field of magnetics. This article will explore choices for magnetoresistive read head materials, with an emphasis on the materials challenges.The recording heads that are used in high-performance disk drives typically consist of separate magnetoresistive read and inductive write heads (see Figure 1) where previously a single inductive head performed both functions. Separation of the two heads allows each to be optimized for their individual function, an essential factor in enabling disk drives to contain gigabytes of storage. The write head is the simpler of the two, consisting of a U-shaped ferromagnet surrounding a set of coils. The ends of the ferromagnet are the magnetic poles defining the write gap. When current passes through the coils, a field bridges the gap, setting the orientation of the magnetization in the media. Information is stored by changing the polarity of the current in order to write a pattern of magnetic domains in the media. The materials used in write poles will be reviewed in the section, Write Head Materials.
A series of amine-functionalized poly(9,9-dihexylfluorene) (PFH) derivatives, PFH-NH
2
F-39-1 (P1), PFH-NH
2
F-19-1 (P2), PFH-NH
2
F-9-1 (P3), and PFH-NH
2
F-17-3 (P4), and PFH-NH
2
F-4-1 (P5), were developed to form organic/inorganic hybrid composites with CdSe/ZnS nanoparticle for polymeric light-emitting diodes (LEDs). The structures and purities of all desired polymers were fully characterized by 1H and 13C NMR, UV−vis and photoluminescent spectroscopy, gel permeation chromatography, elemental analyses. The hybrid nanocomposites were in situ formed through these amino-functionalized polyfluorene derivatives doped with core−shell CdSe/ZnS quantum dots (QDs). The detailed characterizations of their photophysical properties revealed that rapid Förster energy transfer from the conjugated polymers to the red-emitting QDs afforded an efficient red color emission. The preliminary polymeric LEDs fabrication with the configuration of ITO/DB/nanocomposites/Al achieved red emission for the in situ prepared hybrid nanocomposites. The investigation of device performance indicates that these nanocomposites are promising red light-emitting polymeric LED materials with good performance in providing excellent color purity, stability, and robustness. Such strategy provides us a platform to achieve red-emitting hybrid nanocomposites as the active materials for LEDs.
The long-range nature of magnetic dipole interactions leads to a shape dependence of all magnetic properties. In homogeneous ellipsoids, this dependence can be characterized in terms of a simple demagnetizing factor, which depends only on the shape of the body. In all other situations the demagnetizing fields depend on position within the body, and in most cases, also on the magnetic properties of the material. We present calculations on various thin disc-shaped samples, for four different model equations of state, from which demagnetizing corrections in a wide variety of situations can be estimated. The results show that the corrections are generally field and temperature dependent, in contrast to the usual approximation of a constant effective demagnetizing factor. These effects can be quite significant in the analysis of high-resolution magnetic measurements, especially near phase transitions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.