Schematic of
domain wall creep. When a very weak magnetic field or electric
current is applied
to the magnetic wire with domain wall, the domain wall
behaves as an elastic
interface and slowly moves, creeps.
The research group of Professor Hideo Ohno and Associate Professor
Shunsuke Fukami of Tohoku University has studied in detail, a slow change of
microscopic magnetic structures in metallic wires induced by external driving
forces, commonly called "creep" motion. This has allowed them to
clarify the physics of how the driving forces, magnetic fields or electric
currents, act on the magnetic structure.
Previous studies had shown that while the actions of
magnetic fields and currents are the same for metallic materials, they are
fundamentally different for semiconductor materials.
The present study reveals that in cases where the sample
satisfies a certain condition, the current acts on the magnetic structure in a
different manner from the magnetic field case, irrespective of the intricacies
of the material.
Schematic of a
three-terminal memory device with current-induced
domain wall motion.
To write the information, current is applied to
magnetic wire
having domain wall (DW) to drag it.
The development of a high-performance magnetic memory device
(where the magnetic structure is manipulated by current) has been intensively
pursued recently, and the present findings are expected to facilitate the
fundamental understanding to achieve the practical application.
The research group fabricated a wire device consisting of a
ferromagnetic metal CoFeB, and investigated the universality class of a
magnetic domain wall "creep". They evaluated the domain wall velocity
for various magnitudes of magnetic field or electric current while keeping the
device temperature constant, from which they derived the scaling exponent for
the universality class.
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The obtained findings shed light on a statistical physics of
creep motion of elastic interfaces and development of high-performance magnetic
memory devices.