Unconventional bias dependence of tunnel magnetoresistance induced by the Coulomb blockade effect

Temperature dependence of the tunnel magnetoresistance (TMR) was calculated in range of the quantum-ballistic model in the magnetic tunnel junction (MTJ) with embedded nanoparticles (NPs). The electron tunnel transport through NP was simulated in range of double barrier approach, which was integrated into the model of the magnetic point-like contact. The resonant TMR conditions and temperature impact were explored in detail. Moreover, the possible reasons of the temperature induced resonant conditions were discussed in the range of the lead–tunneling cell (TC)–lead model near Kondo temperature. We also found that redistribution of the voltage drop becomes crucial in this model. Furthermore, the direct tunneling plays the dominant role and cannot be omitted in the quantum systems with the total tunneling thickness up to 5–6[Formula: see text]nm. Hence, Coulomb blockade model cannot explain Kondo-induced TMR anomalies in nanometer-sized tunnel junctions.

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Ferromagnetic Single-Electron Transistor with RC Gate

MRS Proceedings ◽

10.1557/proc-746-q2.12 ◽

2002 ◽

Vol 746 ◽

Author(s):

Jun-ichi Shirakashi ◽

Yasushi Takemura

Keyword(s):

Coulomb Blockade ◽

Single Electron ◽

Single Electron Transistors ◽

Tunnel Magnetoresistance ◽

In Series ◽

Gate Potential ◽

Macroscopic Quantum Tunneling ◽

Charge States ◽

Gate Resistance ◽

Electron Transistors

ABSTRACTFerromagnetic single-electron transistors coupled to the controlling gate potential by the gate resistance and gate capacitance in series are studied quantitatively. In this type of the device, several metastable charge states are possible within the Coulomb blockade range. The enhancement and hysteresis of tunnel magnetoresistance on drain and gate voltages are predicted. Inelastic macroscopic quantum tunneling of charge and existence of several charge states play an important role for the unique behavior of the tunnel magnetoresistance. This implies that RC-coupled ferromagnetic single-electron transistors have a new functionality as novel magnetoresistive nanostructure devices.

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Theoretical Study on Tunnel Magnetoresistance Oscillation Due to Coulomb Blockade in Nanoscale Magnetic Tunnel Junction

MRS Proceedings ◽

10.1557/proc-776-q11.18 ◽

2003 ◽

Vol 776 ◽

Author(s):

Yasushi Takemura ◽

Jun-ichi Shirakashi

Keyword(s):

Tunnel Junction ◽

Coulomb Blockade ◽

Theoretical Study ◽

Voltage Dependence ◽

Magnetic Tunnel Junction ◽

Tunnel Magnetoresistance ◽

The Monte Carlo Method ◽

Current Voltage ◽

Coulomb Staircase ◽

Charging Energy

AbstractIn a small magnetic tunnel junction (MTJ) whose charging energy is larger than a thermal energy, the tunnel magnetoresistance (TMR) is enhanced by the Coulomb blockade. Transport properties in a double MTJ were theoretically studied by using the Monte Carlo method. The temperature dependence of current-voltage and TMR characteristics indicated that a small junction with 5 nm electrodes exhibited the Coulomb blockade at 300 K. It was also found that the background charge changed the threshold voltage of the Coulomb blockade. In asymmetric double tunnel junctions, the current-voltage characteristic exhibited a Coulomb staircase and the voltage dependence of the TMR ratio oscillated.

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