Controllable Magnetization Processes Induced by Nucleation Sites in Permalloy Rings
Different arrangements of notches as nucleation sites are demonstrated experimentally and numerically to effectively control the magnetization processes of permalloy rings. In the ring with notches at the same side with respect to field direction, two same-helicity vortex domain walls in the onion s...
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| Published in | Japanese Journal of Applied Physics Vol. 49; no. 2; pp. 023001 - 023001-4 |
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| Main Authors | , , , , , , , |
| Format | Journal Article |
| Language | English |
| Published |
The Japan Society of Applied Physics
01.02.2010
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| Online Access | Get full text |
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| Summary: | Different arrangements of notches as nucleation sites are demonstrated experimentally and numerically to effectively control the magnetization processes of permalloy rings. In the ring with notches at the same side with respect to field direction, two same-helicity vortex domain walls in the onion state lead to two-step switching going through flux-closure state; in the ring with diagonal notches two opposite-helicity vortex domain walls lead to one-step switching skipping flux-closure state. The switching processes are repeatable in contrast to rings without notches where helicites of two vortex domain walls are random so the switching processes can not be controlled. |
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| Bibliography: | SEM pictures of the permalloy rings with notches at the same side (a) and diagonal (b) with respect to the field direction. The notches for both rings are indicated on the figure, and the direction of magnetic field is denoted by an arrow inside each ring. The outer diameter, inner diameter, line width, and thickness of each ring are 8.1 \mbox{$\mu$m}, 5.9 \mbox{$\mu$m}, 1.1 \mbox{$\mu$m}, and 30 nm, respectively, and the radius of each half circle notch is about 270 nm. (c) Schematic picture indicating the length and position of the notches: the length L of the notch is about 540 nm, and the distance h between the notch center and the symmetrical axis indicated by dotted line is 1 \mbox{$\mu$m}. Simulated spin configurations of permalloy rings with notches at the same side (a)--(d) and diagonal (e)--(g) with respect to the field direction. The outer diameter, inner diameter, line width and thickness are 375, 225, 75, and 30 nm, respectively, and the depth of each notch is 15 nm. (h) Schematic picture indicating the length and position of the notches: the length L of the notch is about 30 nm, and the distance h between the notch center and the symmetrical axis indicated by the dotted line is 75 nm. The magnitude and direction of the external magnetic field H are shown inside each ring. The unit cells are reduced in each ring for display purpose. The gray scale represents the magnetic pole density distribution. Simulated hysteresis loops of permalloy rings. (a) The outer diameter, inner diameter, line width and thickness of each ring are 375, 225, 75, and 30 nm, respectively, and the depth of each notch is 15 nm. (b) The outer diameter, inner diameter, line width and thickness of each ring are 600, 360, 120, and 30 nm, respectively, and the depth of each notch is 15 nm. The gray curves correspond to the hysteresis loops for the rings with notches at the same side; the black curves correspond to the hysteresis loops for the rings with diagonal notches. Experimentally obtained magnetoresistance curves of permalloy rings with notches at the same side (a) and diagonal (b) with respect to the field direction. The spatial relationships between the field directions, notches, and Au leads are shown in the insets at right-hand side of each figure. The schematic pictures for the magnetization states are shown in the lower part of each figure. The schematic pictures indicating the existence of the plateau of flux-closure state in the sweep-down processes are given at upper left-hand side of each figure. |
| ISSN: | 0021-4922 1347-4065 |
| DOI: | 10.1143/JJAP.49.023001 |