We fabricated fully epitaxial Fe/ZnO/MgO/Fe magnetic tunnel junctions (MTJs) with low junction resistance-area products (several Ωμm2) and conducted a theoretical estimation of square-low rectifying performance for a terahertz electromagnetic wave. Effective current responsivity up to 0.09 A/W at 1 THz was obtained under zero-bias voltage condition at room temperature. The result is approximately half the value of the best result obtained for experiments in semiconductor-based diodes, performed under similar conditions. The study strongly suggests that this MTJ system has a great potential for the rectifying element of the terahertz wave.
Several researchers have recently studied high-temperature (HT) motor drive systems under harsh temperature environments. We experimentally and numerically investigate iron loss and the magnetic hysteretic properties of amorphous magnetic materials (AMM) at room temperature (RT) and HT under pulse width modulation (PWM) inverter excitation. We demonstrate that the iron loss of AMM core fed by PWM inverter decreases as temperature increases similar like in the sinusoidal case. In addition, the temperature dependence of the B − H hysteresis curves of AMM under PWM inverter excitation relies not only on major loops but also on minor loops. Because the current at 300 ◦C is higher than that at RT, the torque of the motor with AMM at HT becomes large at a few operating points. To realize low iron loss of HT motor drive systems, it is important to reduce eddy current losses of AMM cores at HT under PWM inverter excitation compared with the cases at RT. These results facilitate further research in iron loss reduction of motor systems based on studies of magnetic properties at HT under PWM inverter excitation.