(a) Sketch of the sample fabrication process. Red dots represent Co particles. (b) Current versus bias voltage for Sample 1 at 90 mK. (c) Hysteresis loops in current versus applied magnetic field at −0.1 mV, in sample 1 at 1.3 K and 4.4 K. The current loop at 1.3 K is offset by −0.15 pA for clarity. (d) Magnetic switching field for sample 1 at three different bias voltages/currents and 90 mK. Red (black) lines in (c) and (d) correspond to increasing (decreasing) magnetic field.
(a) and (b) Average switching field versus tunneling current for samples 1 and 2, respectively. Each data point is averaged over approximately 40 hysteresis loops. Insets: Magnetic temperature at the switching field versus tunneling current.
(a) Probability of transitions from the ground state to the ground state and excited states , by an addition of an electron to theminority level j. and 2 represent the magnetic ground state, first, and second magnetic excited state with spin , respectively. Viewed from the left most data points, (red), 0.95 (black), 0.99 (blue), and 0.999 (green) from top to bottom. (b) Probability of a magnetic tunneling transition versus magnetic field. Inset: Increment in magnetic excitation energy upon an addition of an electron to the minority level j versus magnetic field. Black line is the classical energy , while the red line is obtained from the master equation. and in (a) and (b).
(a) Sketch of the classical magnetic excitation energy induced byelectron tunneling and magnetic anisotropy fluctuations. (b) Magnetic excitation energy versus time simulated numerically using Eq. (2) . Black line corresponds to both and . Red line: for both black and red. Blue line: and .
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