Preparation and Properties of Well-Defined Magnetic Particles

MRS Bulletin ◽  
1989 ◽  
Vol 14 (12) ◽  
pp. 35-40 ◽  
Author(s):  
Masataka Ozaki
Keyword(s):  
Drug Delivery Systems ◽  
Magnetic Particles ◽  
Magnetic Interactions ◽  
Recording Media ◽  
Magnetic Media ◽  
Magnetic Recording Media ◽  
Scientific Interest ◽  
Small Particles ◽  
Magnetic Dispersions ◽  
Geomagnetic Fields

Magnetic particles are important not only in the technology, but also in the function of some biosystems. In addition, they are of great scientific interest in developing a better understanding of magnetic phenomena. Ever since magnetic recording media were first prepared, extensive efforts have been made to produce improved magnetic dispersions. The particle s for magnetic media must be of single domain, high saturation magnetization, and proper coercive force. However, the magnetic interactions between such particles are very strong, and stable dispersions are difficult to obtain. Originally, their use was limited to audio tapes, but presently they are employed in a variety of applications. Thus, small particles of different magnetic properties are constituents of magnetic fluids.In 1975, magnetic particles were identified in the bodies of some bacteria, which can navigate along geomagnetic fields. It is also believed that certain animais have the ability to detect a magnetic field due to the presence of magnetic particles in their cells.Techniques are being developed to introduce new functions to materials by incorporating magnetic particles. For example, magnetic particles that are encapsulated by nonmagnetic compounds (e.g. polymers) or particles are used for binding and separating enzymes from reactant mixtures. Efforts are under way to use magnetic particles in drug delivery Systems and for diagnosis.

Patterned Magnetic Media Made by Self-Assembled Block-Copolymer Lithography

MRS Bulletin ◽  
2008 ◽  
Vol 33 (9) ◽  
pp. 838-845 ◽  
Author(s):  
C.A. Ross ◽  
J.Y. Cheng
Keyword(s):  
Magnetic Particles ◽  
The Self ◽  
Recording Media ◽  
Magnetic Media ◽  
Magnetic Recording Media ◽  
Large Area ◽  
Nanoscale Structures ◽  
Lithography Process ◽  
Self Assembled ◽  
Block Copolymer Lithography

AbstractPatterned magnetic recording media, in which data bits are stored in discrete single-domain magnetic particles, have been proposed for the next generation of recording media. To achieve high densities, features with periodicities on the order of 25 nm and below are required over large areas, which is a challenging task for any lithography process. Block copolymers (BCPs), which phase-separate into ordered periodic nanoscale structures, might provide a path to accomplish such patterning. In this article, we describe BCP lithography and show how the self-assembled patterns can be templated to make large-area arrays of nanoscale structures with long-range order.

Crystallization of barium hexaferrite

1992 ◽  
Vol 50 (1) ◽  
pp. 362-363
Author(s):  
Chung-kook Lee ◽  
Yolande Berta ◽  
Robert F. Speyer
Keyword(s):  
Size Distribution ◽  
Raw Materials ◽  
Barium Hexaferrite ◽  
Recording Media ◽  
Magnetic Recording Media ◽  
Promising Candidate ◽  
Crystallization Method ◽  
Temperature Heat ◽  
High Density Magnetic Recording ◽  
Temperature Heat Treatment

Barium hexaferrite (BaFe12O19) is a promising candidate for high density magnetic recording media due to its superior magnetic properties. For particulate recording media, nano-sized single crystalline powders with a narrow size distribution are a primary application requirement. The glass-crystallization method is preferred because of the controllability of crystallization kinetics, hence, particle size and size distribution. A disadvantage of this method is the need to melt raw materials at high temperatures with non-reactive crucibles, e.g. platinum. However, in this work, we have shown that crystal growth of barium hexaferrite occurred during low temperature heat treatment of raw batches.

Grain separation enhanced magnetic coercivity in Pt/Co multilayers.

1993 ◽  
Vol 51 ◽  
pp. 1038-1039 ◽  
Author(s):  
G.A. Bertero ◽  
R. Sinclair
Keyword(s):  
Remanent Magnetization ◽  
Strong Influence ◽  
Uniaxial Anisotropy ◽  
Magnetic Coupling ◽  
Recording Media ◽  
Magnetic Media ◽  
Signal To Noise ◽  
Out Of Plane ◽  
Longitudinal Recording ◽  
The Relationship

Pt/Co multilayers displaying perpendicular (out-of-plane) magnetic anisotropy and 100% perpendicular remanent magnetization are strong candidates as magnetic media for the next generation of magneto-optic recording devices. The magnetic coercivity, Hc, and uniaxial anisotropy energy, Ku, are two important materials parameters, among others, in the quest to achieving higher recording densities with acceptable signal to noise ratios (SNR). The relationship between Ku and Hc in these films is not a simple one since features such as grain boundaries, for example, can have a strong influence on Hc but affect Ku only in a secondary manner. In this regard grain boundary separation provides a way to minimize the grain-to-grain magnetic coupling which is known to result in larger coercivities and improved SNR as has been discussed extensively in the literature for conventional longitudinal recording media.We present here results from the deposition of two Pt/Co/Tb multilayers (A and B) which show significant differences in their coercive fields.

Structural Investigation of Iron Particles Used for Magnetic Recording Media

1980 ◽  
Vol 38 ◽  
pp. 406-407
Author(s):  
Alfred Baltz
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Microscope ◽  
Structural Investigation ◽  
Magnetic Interaction ◽  
Recording Media ◽  
Magnetic Recording Media ◽  
Recording Medium ◽  
Iron Particles ◽  
Transmission Electron

As part of a program to develop iron particles for next generation recording disk medium, their structural properties were investigated using transmission electron microscopy and electron diffraction. Iron particles are a more desirable recording medium than iron oxide, the most widely used material in disk manufacturing, because they offer a higher magnetic output and a higher coercive force. The particles were prepared by a method described elsewhere. Because of their strong magnetic interaction, a method had to be developed to separate the particles on the electron microscope grids.

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