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Posted: November 22, 2007

Nanotechnological magnets will bring smaller and more powerful hard disks

(Nanowerk News) Magnetic materials, also known as magnets, have a wide range of applications in daily life. They are part of the core of electric engines, from those used in cars to CD systems. Computers´ hard disks are made of a magnetic material, very useful in medicine for imagenology systems, as a contrast element in nuclear magnetic resonance measurements and computerized axial tomographs.
The Institute of Materials and Reagents (IMRE) of the Universty of Havana, with the contribution of the Technical University of Vienna and the Federal University of Rio Grande do Sul in Brazil are carrying out a micro-structural study of two types of magnetic materials: Magnetically hard materials with submicronic micro-structure and nano-particulate systems with supersoft magnetic or superparamagnetic response.
Transmission Electronic Microscopy
“The common point of the proposal, according to Dr Ernesto Estévez Rams, main author of the research work, is the transmission electronic microscopy (TEM) study of magnetic materials that show the occurrence of a nanometric microstructure, determinant in the magnetic behaviour”. As this micro-structure appears the grain size reduces to the order of nanometres and the intrinsic properties for volumetric materials stop behaving the same way.
“The study is focused in new generation magnets manufactured with nano-technological methods, this is, magnets whose components have been designed on a scale one hundred thousand times thinner than human hair”. This work intends to understand in depth the composition of this type of materials in order to find optimization channels to make them more suitable for different applications.
It is important to know the relationship between microstructure and physical properties, and here is where the contribution of this research work lies. It was possible to determinate for the first time the mechanism of anomalous growth in HDDR-NdFeB materials, consisting in the abundant growth of certain parts of the material at the expense of others. This phenomenon brings as a consequence the decrease of its physical properties; therefore, clarifying the mechanism of this anomalous growth is an essential step for its later solution.
Another aspect of the research work, which resulted in the generation of a patent, was the microstructural behaviour of Barium Hexaferrite Nanoparticles and its generation route. This study was carried out under different synthesis conditions, and for the first time, it was possible to reduce the temperature to 250 C. The manufacture process was modified and material dust was obtained with a well-controlled particle size, which reached the size of several nanometres. This type of materials are considered excellent means for information storage, as their use can multiply several times the capacity of current hard disks.
Finally, they studied the nanogranular microstructura of the superparamagnetic system Co-Cu and they identified for the first time spinoidal decomposition as an essential mechanism in the system magneto-electric response. This type of magnetic material is used in hard disks´ reading and writing heads; therefore, improving their properties contributes to the future manufacture of smaller heads which are able to read smaller information units. “Spinoidal decomposition was identified for the first time as an essential mechanism in the system magneto-electric response, opening a new research line”, says Dr Estévez Rams.
Source: University of Granada
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