Movement of a DW through a loop with one cusp for the rotating magnetic field in the ccw direction in steps of 90°. The magnetization state in the loop and the DW position is indicated by black arrows and a black line, respectively. The field angle of the rotating external field is given as number and illustrated with the red centered arrow.
Magnetic configuration of the magnetization in the cusp during the movement of a DW through the cusp for μ 0 Hrot = 35 mT and a nanowire width of w = 160 nm.
The minimum field Hmin and the maximum field Hmax as well as the operation margin ΔH is plotted in dependence on (a) the apex angle theta, (b) the geometric ratio l/w and (c) the thickness of the nanowires t. The thickness in (a)is t = 20 nm and the ratio in (b) is l/w = 2. Note the interrupted ordinate in (b). l and w are defined in Fig. 2(i). The error bars are smaller than the symbol sizes.
(a) Movement of a DW over an isolated cusp for μ 0 H = 16 mT rotated in ccw-direction. Signal jump from L to M indicates the motion to the cusp and the jump from M to H the motion from the cusp to the next corner (Vcc = 2 V). Inset: (b) Scanning electron microscope picture of the cusp under investigation. The visible grain structure represents the microstructure of the top 200 nm Au electrode covering the whole cusp. (c) and (d) are enlarged micrographs from the region around the top and bottom of the cusp.
Read out scheme in a Wheatstone half bridge geometry. The magnetization direction with respect to the reference direction (shown as red arrow and marked with Ref) determines the resistance state of the GMR nanowire. Blue and orange represent low and high GMR values, respectively. The relative bridge voltage Ub is given for the four possible cases. H (L) is a higher and (lower) voltage level compared to .
Magnetization configurations for a loop containing 6 cusps, which is filled with 4 DWs in a chain. (a)–(e) show the DW positions (black stripe) for consecutive rotations of 90°, i.e., a quarter turn. (f) shows the positions of the Gnd (white), Vcc (black) and read-out (gray) contact pads, which are necessary for a useful readout. The resistance state of the GMR nanowire is color coded in blue (low resistance) and orange (high resistance). The possible outputs of Ub 1 and Ub2 are summarized in Table I.
Magnetization configurations for a loop containing 1 cusp, which is filled with 1 DW. (a)–(g) show the DW position (black stripe) for consecutive rotations of 90°, i.e., a quarter turn. (h) shows the positions of the Gnd (white), Vcc (black) and read-out (gray) contact pads, which are necessary for a useful readout. The possible outputs of Ub 1, Ub2 , and Ub3 are summarized in Table II.
Optical micrograph of the current conducting layer above six GMR nanowires 1 − 6 (part from a sensor with 6 loops). The Oersted field created by the current through the Au-conductor is used to pin a DW in each GMR nanowire in the vicinity of the conductor.
Outputs of the contact pads Ub 1 and Ub 2 in Fig. 7(f) in dependence on the number of field rotations. The voltage levels L, M, and H are defined in Fig. 6. The digital output of the sensor is shown in the last column.
Outputs of the contact pads Ub 1, Ub 2, and Ub 3 in Fig. 7(h) in dependence on the number of field rotations. The voltage levels L, M, and H are defined in Fig. 6.
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