We have studied the current induced domain wall motion by using patterned U geometry. The observation of two magnetic states of the U-pattern was evidenced. One is the vortex domain wall at the center of semicircular arc in U-pattern and the other is the continuous magnetic state without wall. We investigated the influence of the positive and negative dc current injection on domain wall motion before switching field with density on the order of similar to 10(7) A/cm(2). The critical current varied dramatically as the bias field is close to the switching field and only gradually as the field is far away from the switching field. (c) 2005 American Institute of Physics
Micron size NiFe wire having a patterned shape of semicircle in series was fabricated. Magnetoresistance of the wire has been studied from 10 to 300 K. Domain wall resistivity is nearly independent of the temperature; however, the domain wall switching field decreases relatively rapidly with increasing temperature. We have observed experimentally two distinct domain structures at the corners of the NiFe semicircle-ring patterned wire at remanence after longitudinal and transverse saturation fields. We can explain successfully the magnetization reversal process on the magnetoresistance loops by the contribution from anisotropic magnetoresistance and magnetic domain configuration.
The domain wall resistivity of the patterned Ni80Fe20 zigzag wires has been studied as functions of the number of corners and temperature in zigzag wires. The quantitative ratio of domain wall magnetoresistance (MR) is estimated by two methods. One is the discontinuous jump that represent the domain state sweep between two states in MR curve. The other is the angular dependence on the resistance at remanent state. The ratio of domain wall MR increased when domain wall number density over total wire length (DWs/L) changed from 12/73 to 34/73 with film thickness 40 nm at 10-300 K. Especially, the ratio of. domain wall MR decreased slightly as the temperature ranged from 10 to 300 K. The anisotropic magnetoresistance (AMR) has been subtracted in the calculation. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
We have investigated the magnetization reversal process of the disk-, ring-, and center dot ring-patterned Ni80Fe20 wires. For the fields applied perpendicular to the wire direction, interesting shape dependent magnetoresistance (MR) ratios were found. The MR ratios were varied from 0.8%, 0.65%, and 0.4% at room temperature and 1.7%, 1.5%, and 1.1% at 10 K for the disk-, ring-, and center dot ring-patterned wires. For the same wires, the switching field is reduced from −170, −110, and −90 Oe at room temperature to −140, −70, and −20 Oe at 10 K. These results were due to the shape anisotropy and domain-wall motion. The anisotropy MR (AMR) ratios measured at 10 K of the disk-, ring-, and center dot ring-patterned wires were 1.9±0.1%, 1.7±0.1%, and 1.3±0.1%, respectively, it is almost even the same (1.1±0.1%) at room temperature. We have observed that the center dot reduces the MR ratio and increases magnetic saturation field of the nanosize Ni80Fe20 wires.
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