Physical Society Colloquium
Interview for Faculty Position
What causes magnetization relaxation in ferromagnetic
transition metals?
Snorri Ingvarsson
IBM Research
Yorktown Heights
Much like resistance is to an electric circuit, magnetization relaxation is
what restores the magnetization of a ferromagnet to equilibrium when the
external stimulus (magnetic field) becomes quiescent. The mathematical
equation governing magnetization dynamics in ferromagnets is the
Landau-Lifshitz equation, where magnetization relaxation is usually taken
into account as a phenomenological damping constant (Gilbert damping). In
designing magnetoelectronic devices such as magnetic random access memory, it
is obviously very important to understand what lies behind the Gilbert
damping constant, and to understand how it can be modified. But what is this
Gilbert damping really? In our experimental studies of magnetic thin films we
have found that there is a strong correlation between their electrical
resistance and Gilbert damping, indicating that the relationship between the
two is much closer than the simple analogy mentioned above. It suggests that
the underlying mechanism of Gilbert damping is the interaction between
conduction electrons in the magnet and its magnetization. This interpretation
has helped provide an understanding of two other sets of results. In one case
Gilbert damping in a thin magnetic film was affected dramatically by
adjoining it with certain nonmagnetic transition metal layers. In the other
case damping was increased by alloying with certain transition metal
elements.
Tuesday, March 18th 2003, 16:00
Ernest Rutherford Physics Building, R.E. Bell Conference Room (room 103)
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