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.