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Magnetic Probe For Rocks, Recordings, Nanotechnology

Hysteresis curves are used in many different fields of science and engineering as a means of characterizing the magnetic properties of natural and synthetic materials. Although a typical hysteresis curve may consist of several hundred data points, researchers typically extract only a few numbers from these curves. These numbers provide information about the average magnetic properties of the material in question. Researchers at UC-Davis have recently developed a technique that allows them to determine the distribution of magnetic properties within a material, rather than just the average value. The technique uses partial hysteresis curves to produce a First-Order Reversal Curve (or FORC) diagram. A FORC may provide considerably more information than a single hysteresis curve, such as details about the composition and size distribution of the magnetic particles and their interactions. The FORC method has been used for studying the magnetic properties of natural geologic samples; however, the technique has potential applications to many types of magnetic materials, and it is already being used to study magnetic nanostructures, such as multilayer thin films and advanced magnetic media.
David - May 19, 2003
A technique for studying the magnetic properties of rocks developed by earth scientists at UC Davis is drawing attention from other scientists and the magnetic recording industry.

An international group of scientists recently met in Davis to discuss the First Order Reversal Curve (FORC) method and its applications for studying million-year old rocks, thousand-year old lake sediments, modern hard drives and wholly new kinds of materials made in the lab.

Magnetic materials are made up of grains that act as tiny magnets. The size and orientation of these grains determines the magnetic properties of the whole material. Magnetic tapes and hard drives use those magnetic grains to store information.

The FORC method involves subjecting materials to a series of switching magnetic fields. How they respond gives information about the size, orientation and behavior of magnetic grains in the material.

Rocks store magnetic information for millions of years, said UC Davis geophysicist Ken Verosub, who with physicist Christopher Pike and geologist Andrew Roberts (now at the University of Southampton, England) originally developed the method.

Grains in rocks are magnetized by the Earth's magnetic field. When the Earth's field changes, some of the grains may change orientation, Verosub said. On a more recent timescale, changes in climate over thousands of years leave magnetic traces in the sediment on the floor of ancient lakes and seas.

FORC helps geologists understand how these magnetic signals are recorded in rocks and sediments. It also provides information about magnetic interactions between grains which could be useful for developing better hard drives and magnetic storage devices.

Verosub and Pike have joined with physicists Kai Liu, Richard Scalettar and Gergely Zimanyi to explore these new applications of the method. Scalettar, Zimanyi and Pike are using simulations and computer modeling to investigate the underlying physics behind the method.

Liu uses FORC to study novel materials, called nanomaterials because they are made up of extremely small layers, dots or other structures, that he makes in the lab. Such materials have novel properties compared to bulk materials because of their extremely small dimensions.

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Pioneering New Applications for Carbon Nanotubes
New York - May 13, 2003
IBM today announced it created the world's smallest solid-state light emitter. This research breakthrough the first, electrically-controlled, single-molecule light emitter demonstrates the rapidly improving understanding of molecular devices.


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