|Direct Imaging of Asymmetric Magnetization Reversal| The
phenomenon of exchange bias has transformed how data is read on
magnetic hard disks and created an explosion in their
information storage density. However, it remains poorly
understood, and even the fundamental mechanism of magnetic
reversal for exchange-biased systems in changing magnetic fields
is unclear. By using x-ray photoemission electron microscopy at
the ALS to directly image the magnetic structure of an exchange-
biased film, a team from the University of Washington and the
Stanford Synchrotron Radiation Laboratory has identified
separate magnetic-reversal mechanisms in the two branches of a
hysteresis loop. This advance in fundamental understanding will
provide new insights for developing the next generation of
information storage and sensing devices where exchange bias is
expected to play a critical role. There are two basic energies
involved in the manipulation and control of the magnetic
properties of materials. Exchange controls magnetic