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This detailed report delves into the resistance measurements and scaling of nanoscale junctions, showcasing variations in resistance values, hysteresis curves, and field dependence. The analysis includes identification of low resistance junctions, scaling patterns, and typical/non-typical hysteresis behaviors. Additionally, the report explores serpentine patterns and the impact of electrode characteristics on resistance. Overall, differences in resistance across different samples and the stability of resistance peaks are discussed.
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Q2 Resistance Overview Column 25 contains other measurements 300 nmx 600 nm 450 nmx 900 nm • Two rows have relatively low resistance (M and N). • The complete block on the right hand side has low resistance and only 3 opens. • Red lower right corner indicates that MR was tested.
Q2 Resistance Scaling(all points) Detail All R • If the resistance is plotted for all measured points, no scaling is visible.
Q2 Resistance Scaling(manually selected points, all points) • This plot shows the resistance scaling for the junctions that seemed to be good. • There could be scaling with area (see detail next slide).
Q2 Resistance Scaling(manually selected points, detail) • There could be some scaling, at least the points are not randomly distributed. • The red square indicates the good junction. • The line indicates a possible scaling law.
Q2 Typical Hysteresis Curves C23 200 nm x 300 nm • Many junctions show a magnetical signal. • It is never hysteretic, but always single spikes up or down at about 80 mT. • The next slide just shows many of these curves for different samples.
Q2, Collection of Hysteresis Curves • No selection, these are the curves like measured • Most of them show some MR M23: 300 x 600 N22: 450 x 900 M22: 300 x 600 G22: 180 x 260 J22: 160 x 280 H22: 180 x 200 M21: 300 x 600 N16: 450 x 900 Continued on next page N21: 450 x 900
Q2, Collection of Hysteresis Curves, cont. F22: 180 x 300 E22: 180 x 340 C22: 200 x 300 A22: 250 x 400 B22: 200 x 400 B22: 200 x 400 • The curves were not selected by hand. • Most have peaks at around +- 80 mT. • The peaks show both signs, sometimes for the same junction. • The sweeps are not always reproducible (see e.g. B22; domain walls?).
Q2 Field dependence 22B: 200 x 400 In plane Perp. plane Peaks switched sign. • The measurement was repeated twice for in-plane and out-of-plane fields. • The peaks shift, but are not reproducible for one field direction either.
Q2 Non-typical Hysteresis Curve D22: 200 x 350 0.89% MR • This is the only good junction. • The resistance is not different from other junctions, it is in the middle of the other junctions.
Q2 Serpentine Pattern • Magnetoresistance of the serpentine pattern on Q2 with some initial drift.
Q2 After Top ElectrodeResistance Overview, High-speed 4-point • Sample 26A has hysteretic behaviour.
Q2 After Top Electrode High-speed 4-point 26A: 150 x 300 • 0.2% MR. • These measurements cannot be done with the picoprobes.
Q2 After Top ElectrodeCurrent Sweep 26A: 150 x 300 High-speed 4-point Corrected for heating Raw data • Current Sweep does not indicate current-induced excitations or switching.
Q3 Resistance Overview • Resistance is worse than on Q2. • Again, junctions with similar resistance cluster.
Q3 22N Hysteresis 30 sweeps averaged • The peak appears on Q3, too. • Averaged over 30 sweeps the peak disappears, because it is not stable.
Q3 MR Serpentine Pattern • Magnetoresistance of the serpentine pattern on Q3 looks worse than on Q2.
