11.2 Nanochannel Templates Obtained with Top-Down Synthesis Methods
377
Fig. 11.6 Comparison of the
magnetic behavour of
single-crystalline and
polycrystalline Ni nanowires
(see filled and empy
symbols, respectively). The
external magnetic field is:
a parallel to the nanowire
axis (i.e., perpendicular to
the plane of the template);
b perpendicular to the
nanowire axis (i.e., in-plane
with respect to the substrate).
Reprinted from [71].
Copyright (2007), with
permission from Elsevier
with either a through bath pH regulation [51, 52, 74] or with optimized electrodeposition parameters in direct current [28, 58, 69, 73–75] and pulse-plating [54, 55, 72]
modes. As a result of the optimization of the nanowire structure, the coercivity of
the nanowire arrays along the nanowire axis direction can be as high as 4 kOe [101,
169], more than an order of magnitude larger than the coercivity of their bulk counterpart. For Co–Pt alloys obtained with annealing of Co/Pt multilayered nanowires,
coercivity in the wire axis direction can be larger than 10 kOe [162].
The elucidation of the magnetization behaviour of compositionally modulated
nanowires is more difficult than that of their homogeneous counterparts. The shape
anisotropy of segments with lower aspect ratio affects the coercivity, but the direction
of the coercivity change is ambiguous. The squareness of the magnetization curves
decreases with the nanowire segmentation [19, 150]. If the nanowire is multilayered
with thickness much less than the wire diameter for both the magnetic and nonmagnetic layers, the competition of various anisotropy contributions usually leads to
a more even magnetization for in-plane and perpendicular-to-plane directions than
for homogeneous wires. If the thin magnetic layers are separated by non-magnetic
segments much longer than the wire diameter, the shape anisotropy of the single
magnetic layers becomes dominant [150].
Electrical transport properties. The study of the electrical transport properties
of nanowires has always been important because thin nanowires are a very good
approximation of one-dimensional materials. Hence, their study is crucial for testing
theories referring to one-dimensional systems.
The study of the electrical transport properties of nanowires can be carried out in
three ways, namely as nanowire array within the template, single nanowire within the
template and single nanowire after being removed from the template. For measuring
377
Fig. 11.6 Comparison of the
magnetic behavour of
single-crystalline and
polycrystalline Ni nanowires
(see filled and empy
symbols, respectively). The
external magnetic field is:
a parallel to the nanowire
axis (i.e., perpendicular to
the plane of the template);
b perpendicular to the
nanowire axis (i.e., in-plane
with respect to the substrate).
Reprinted from [71].
Copyright (2007), with
permission from Elsevier
with either a through bath pH regulation [51, 52, 74] or with optimized electrodeposition parameters in direct current [28, 58, 69, 73–75] and pulse-plating [54, 55, 72]
modes. As a result of the optimization of the nanowire structure, the coercivity of
the nanowire arrays along the nanowire axis direction can be as high as 4 kOe [101,
169], more than an order of magnitude larger than the coercivity of their bulk counterpart. For Co–Pt alloys obtained with annealing of Co/Pt multilayered nanowires,
coercivity in the wire axis direction can be larger than 10 kOe [162].
The elucidation of the magnetization behaviour of compositionally modulated
nanowires is more difficult than that of their homogeneous counterparts. The shape
anisotropy of segments with lower aspect ratio affects the coercivity, but the direction
of the coercivity change is ambiguous. The squareness of the magnetization curves
decreases with the nanowire segmentation [19, 150]. If the nanowire is multilayered
with thickness much less than the wire diameter for both the magnetic and nonmagnetic layers, the competition of various anisotropy contributions usually leads to
a more even magnetization for in-plane and perpendicular-to-plane directions than
for homogeneous wires. If the thin magnetic layers are separated by non-magnetic
segments much longer than the wire diameter, the shape anisotropy of the single
magnetic layers becomes dominant [150].
Electrical transport properties. The study of the electrical transport properties
of nanowires has always been important because thin nanowires are a very good
approximation of one-dimensional materials. Hence, their study is crucial for testing
theories referring to one-dimensional systems.
The study of the electrical transport properties of nanowires can be carried out in
three ways, namely as nanowire array within the template, single nanowire within the
template and single nanowire after being removed from the template. For measuring