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Shvoong Home>Science>Physics>Fine particle spinels Summary

Fine particle spinels

Book Summary   by:Gayathrishenoy     Original Authors: Gayathri shenoy; Santhosh shenoy
  • Summary rating: 5 stars (5 Ratings)
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  • words:600 
ª
 
The classification of magnetic materials was made according to their magnetic structure. The two possible atomic origins of magnetism, which lead to the magnetization of magnetic substances, are the orbital motion and spin motion of electrons. An atom, which has a magnetic moment, caused by spin or by orbital motion of electrons or by both is generally called a magnetic atom. Basically magnetic materials can be classified in to five categories namely diamagnetic, paramagnetic, ferromagnetic, antiferromagnetic and ferrimagnetic. Of these ferro and ferri magnetic materials have great commercial importance due to their unique properties like appropriate magnetic characteristics, high resistivity and low eddy current losses. They are employed in various devices like television sets, transformer cores, loud speakers, telephone receivers and memory devices. Actually the search for ferromagnetic materials of unusually high resistivity resulted in the emergence of ferrites. Ferrites crystallize into the spinel structure, which is named after the mineral spinel, MgAl2O4. Fine particles with size in the nanometric scale have made greatest revolution in materials science research. Current research is devoted to tailor the microstructure at the nanometric scale and correlate it to the macroscopic properties. Some of these anomalous or enhanced properties are: giant magnetoresistance (GMR) and extraordinary Hall effect metallic systems; large tunnelling magnetoresistance (TMR) in insulating materials; remanence, coercitivity and magnetocaloric effect enhancements; glassy behaviour and quantum tunnelling of the magnetization. These new properties make nanomaterials have an enormous technological impact, e.g. in the new generation of ultra-high density magnetic information storage devices, and on some industrial technologies (e.g. magnetic sensors, refrigerant materials and permanent magnets). Besides, magnetic particles and clusters of nanometric size posses an increasing importance in quantum computing, and as diagnostic and therapeutic tools in medicine and other life sciences. High-energy ball milling is being extensively employed as an alternate route to obtain novel fine particle systems through solid-state reactions. The high-energy ball milling is an excellent tool to produce fine particle materials with a wide range of particle sizes. The decrease in particle size with milling occurs which is due to the fact that the kinetic energy generated by the series of collisions among balls is transferred to the powder taken in the vial. In this work, fine particles of zinc ferrite and zinc aluminate were prepared by coprecipitation method and subjected to high-energy ball milling. Structural, magnetic, Mössbauer and electrical studies on zinc ferrites were carried out and correlated. Structural and electrical studies of zinc aluminate were also carried out, compared with zinc ferrite results and correlated.
Published: August 22, 2007   
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