The magnetic field resolution of the tunnel magneto-resistive (TMR) sensors has been improving and it reaches below 1.0 pT/Hz0.5 at low frequency. The real-time measurement of the magnetocardiography (MCG) and the measurement of the magnetoencephalography (MEG) have been demonstrated by developed TMR sensors. Although the MCG and MEG have been applied to diagnosis of diseases, the conventional MCG/MEG system using superconducting quantum interference devices (SQUIDs) cannot measure the signal by touching the body, the body must be fixed, and maintenance costs are huge. The MCG/MEG system with TMR sensors operating at room temperature have the potential to solve these problems. In addition, it has the great advantage that it does not require a special magnetic shielded room. Further developments are expected to progress to maximize these unique features of TMR sensors.

We propose a compact magnetic tunnel junction (MTJ) model for circuit simulation by de-facto standard SPICE in this paper. It is implemented by Verilog-A language which makes it easy to simulate MTJs with other standard devices. Based on the switching probability, we smoothly connect the adiabatic precessional model and the thermal activation model by using an interpolation technique based on the cubic spline method. We can predict the switching time after a current is applied. Meanwhile, we use appropriate physical models to describe other MTJ characteristics. Simulation results validate that the model is consistent with experimental data and effective for MTJ/CMOS hybrid circuit simulation.

An energy-efficient nonvolatile FPGA with assuring highly-reliable backup operation using a self-terminated power-gating scheme is proposed. Since the write current is automatically cut off just after the temporal data in the flip-flop is successfully backed up in the nonvolatile device, the amount of write energy can be minimized with no write failure. Moreover, when the backup operation in a particular cluster is completed, power supply of the cluster is immediately turned off, which minimizes standby energy due to leakage current. In fact, the total amount of energy consumption during the backup operation is reduced by 66% in comparison with that of a conventional worst-case-based approach where the long time write current pulse is used for the reliable write.

In this paper, we propose a new low power nonvolatile counter unit based on Magnetic Tunnel Junction (MTJ) with fine-grained power gating. The proposed counter unit consists of only a single latch with two MTJs. We verify the basic operation and estimate the power consumption of the proposed counter unit. The operating power consumption of the proposed nonvolatile counter unit is smaller than the conventional one below 140 kHz. The power of the proposed unit is 74.6% smaller than the conventional one at low frequency.

In order to realize Integrated Circuits (IC) with operation over the 10 GHz range, conventional CMOS logic faces critical issues, such as increasing power consumption, and difficulty to aggressively scale the device size and so on. To overcome this issue, we have proposed Current Controlled-MOS Current Mode Logic (CC-MCML) to realize the reduction of power consumption and the enhancement of the operation speed in logic circuits without scaling the gate length of the MOSFET, and confirmed the performance of these circuits both theoretically and experimentally. In the CC-MCML it is extremely important to control the input voltage of the MOSFET used as the constant current source in order to make the base voltage of the input signal and the output signal equivalent. In this paper, we propose CC-MCML/MTJ (Magnetic Tunnel Junction) circuit, which is one type of nonvolatile memory hybrid circuit technology. A more stable and precise operation is realized by cutting the range of the input voltage of the constant current source, and it is shown that the operation of CC-MCML/MTJ Hybrid Circuit enables us to suppress the base voltage difference due to the Vth fluctuation in comparison with the conventional CC-MCML. These results imply the high potential of Si-CMOS/Spintronics Hybrid technologies for future IC.

In this paper, it is shown that our fabricated MTJ of 60180 nm2, which is connected to the MOSFET in series by 3 levels via and 3 levels metal line, can dynamically operate with the programming current driven by 0.14 µm CMOSFET. In our measurement of transient characteristic of fabricated MTJ, the pulse current, which is generated by the MOSFET with an applied pulse voltage of 1.5 V to its gate, injected to the fabricated MTJ connected to the MOSFET in series. By using the current measurement technique flowing in MTJ with sampling period of 10 nsec, for the first time, we succeeded in monitor that the transition speed of the resistance change of 60180 nm2 MTJ is less than 30 ns with its programming current of 500 µA and the resistance change of 1.2 kΩ.

In this paper, we have succeeded in the fabrication of high performance Magnetic Tunnel Junction (MTJ) which is integrated in CMOS circuit with 4-Metal/ 1-poly Gate 0.14 µm CMOS process. We have measured the DC characteristics of the MTJ that is fabricated on via metal of 3rd layer metal line. This MTJ of 60180 nm2 achieves a large change in resistance of 3.52 kΩ (anti-parallel) with TMR ratio of 151% at room temperature, which is large enough for sensing scheme of standard CMOS logic. Furthermore, the write current is 320 µA that can be driven by a standard MOS transistor. As the results, it is shown that the DC performance of our fabricated MTJ integrated in CMOS circuits is very good for our novel spin logic (MTJ-based logic) device.