  The electrical conductance G of magnetostrictive nanocontacts made from
Galfenol Fe73Ga27 can be reproducibly switched between on and off states in a
low magnetic field of 20 to 30 mT at 10 K. The switching behavior is in
agreement with the magnetic field dependence of the magnetostriction inferred
from the magnetization behavior, causing a positive magnetostrictive strain
along the magnetic field. The repeated magneticfield cycling leads to a stable
contact geometry and to a robust contact configuration with a very low
hysteresis of 1 mT between opening and closing the contact due to a training
effect. Nonintegral multiples of the conductance quantum G0 observed for G is
greater than G0 are attributed to electron backscattering at defect sites in
the electrodes near the contact interface. When the contact is closed either
mechanically or by magnetic field, the conductance shows an exponential
behavior below G0 due to electron tunneling. This allows to estimate the
magnetostriction at 10 K. The results demonstrate that such magnetostrictive
devices are suitable for the remote control of the conductance by low magnetic
fields in future nanotechnology applications.
