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Magnetism - Some Current Research Trends In Magnetism

magnetic field —the systems

Ideally pure magnetic systems have provided the most extensively investigated models of the large scale collective behavior of atoms and electrons that occur in the vicinity of the critical point of phase transitions. More recent studies have unearthed fascinating effects caused by the intentional introduction of impurities and defects into random locations in the atomic lattice of a magnetic material. For example, these random magnetic systems display transitions to states of order that have no counterparts in pure systems, because pure systems are, by necessity, always close to thermodynamic equilibrium or stability. For these reasons there is now intense interest and research activity in disordered systems, and random magnets provide ideal model systems for such investigations.

An area of intense current activity centers around the search for a likely magnetic pairing force in the high temperature ceramic superconductors that were discovered in 1987 by the German-Swiss team of Georg Bednorz and Karl Alexander Muller. A superconductor achieves a zero resistance state by means of a force field that pairs up the conducting electrons within its atoms. The new ceramic materials are antiferromagnets in their undoped state, but on doping start to superconduct at temperatures that are over 182°F (83°C) warmer than conventional pure metal and alloy superconductors.

The effects of extremely high magnetic fields on the properties of condensed matter continues to be an area of high interest. New research areas, such as the search and study of magnetism in organic matter, and the study of diamagnetism and novel magnetic effects in the recently synthesized nanometer-sized (a nanometer is equal to 10-9 meter) carbon tubes, are of increasing interest to physicists and material scientists.

Resources

Books

Chikazumi, S. Physics of Magnetism. New York: John Wiley & Sons, Ltd., 1984.

Newton, R.G. What Makes Nature Tick? Cambridge: Harvard University Press, 1993.

Periodicals

Clarke, J. "SQUIDs." Scientific American (August, 1994): 46-53.

Cox, D.L. and M.B. Maple. "Electronic Pairing in Exotic Superconductors." Physics Today (1995): 32-40.

"Materials Science in High Magnetic Fields." Materials Research Society Bulletin 27 (1993).


Zafar Iqbal

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Curie temperature

—The temperature at which magnetic domains become randomized.

Diamagnetism

—The negative response of matter to an applied magnetic field that prevents the penetration of the field into its interior.

Electromagnetism

—The unified electrical and magnetic field of force generated by the passage of an electric current through matter.

Ferrimagnetism

—A strong form of magnetism that occurs with antiparallel alignment of unequal magnetic spins.

Ferromagnetism

—A strong form of magnetism that occurs with the parallel alignment of equal magnetic spins.

Geomagnetism

—The magnetism displayed by the earth that is probably caused by the electric fields generated in its central liquid core by its rotation.

Magnetic susceptibility

—The response of a system to an applied magnetic field; it is a dimensionless quantity that is equal to the ratio of the magnetic moment to the applied field intensity.

Magnetometer

—Instrument used to detect and measure magnetic field strengths.

Phase transition

—The phenomenon of a reversible transformation of one state to another state of matter.

Spin

—The magnetic moment or angular momentum due to the rotation of electrons.

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