Magnetic cylindrical nanowires with single modulated diameter

Nucleation and propagation of a domain wall along a modulated wire as a function of its geometry has been investigated. In all the cases, nucleation began at the thicker section and propagated toward the thinner section, regardless of the reversal mode. At the interface, the wall was pinned and a higher nucleation field was required to continue the propagation of the wall. This behavior led to the existence of two nucleation fields along each branch of the hysteresis curve.

Figure 1

Geometrical parameters of a nanowire with modulated diameter.

Figure 2

(Color online) Hysteresis curves for modulated wires with $d_1=65\text{nm}$, $d_2=130\text{nm}$, and $l_1=500\text{nm}$, 800 nm. $l=1.1\mu \text{m}$. The dots represent three different times whose magnetization profiles are illustrated in Fig. 3

Figure 3

(Color online) Magnetization profile for $d_1=65\text{nm}$, $d_2=130\text{nm}$, $l_1=800\text{nm}$, $l_2=200\text{nm}$, and $l=1.1\text{nm}$. The curves represent ${\mu }_i=m_i/m$, $i=x$ (dashed line), $y$ (dotted line), and $z$ (solid line), which are the average values of the magnetic-moment components relative to their saturation value.

Figure 4

(Color online) Hysteresis curves for modulated wires with $d_1=32.5\text{nm}$, $d_2=65\text{nm}$, and $l_1=500\text{nm}$, 800 nm. $l=1.1\mu \text{m}$.

Figure 5

(Color online) Magnetization profile for $d_1=32.5\text{nm}$, $d_2=65\text{nm}$, $l_1=800\text{nm}$, $l_2=200\text{nm}$, and $l=1.1\text{nm}$. The curves represent ${\mu }_i=m_i/m$, $i=x$ (dashed line), $y$ (doted line), and $z$ (solid line), which are the average values of the magnetic-moment components relative to its saturation value.

Figure 6

(Color online) Hysteresis curves for modulated wires with $d_1=30\text{nm}$, 45 nm, 60 nm, and $d_2=130\text{nm}$. $l_1=1000\text{nm}$, and $l_2=200$. $l=1.3\mu \text{m}$.

Figure 7

(Color online) Magnetization profile for $d_1=45\text{nm}$, $d_2=120\text{nm}$, $l_1=1000\text{nm}$, $l_2=200\text{nm}$, and $l=1.3\text{nm}$ at $H_a=-0.3\text{kOe}$. The curves represent ${\mu }_i=m_i/m$, $i=x$ (dashed line), $y$ (doted line), and $z$ (solid line), which are the average values of the magnetic-moment components relative to the saturation value.

Figure 8

(Color online) Hysteresis curves for modulated wires with $d_1=30\text{nm}$, $d_2=45\text{nm}$, and $l_2=308\text{nm}$. $l=1.1\mu \text{m}$.