Magnetic field measurement near a superconducting film using a 2-dimensional field-dependence of Josephson current through a Nb tunnel junctions sensor.

Two-dimensional (2-D) magnetic field dependences of Niobium/niobium tunnel junction current Ic were first used in order to measure the magnetic field near the superconducting film. The 2-D magnetic field dependences of superconducting Josephson current Ic through the niobium/niobium tunnel junction can be changed by the external magnetic field. So, we measured the magnetic field using this superconducting tunnel junction fabricated by DC-magnetron apparatus as a magnetic sensor. The 2-D magnetic field dependences of Ic through the junction without and with the Nb thin-film sample were compared. With the Nb thin-film sample, extension of the characteristics in the perpendicular direction Hz to the sample was observed because of the Meissner effect of the superconducting thin-film sample. Moreover, the magnetic field Hz perpendicular to the Nb thin-film sample has been added in the triangle shape as a following sequence: (0)-(1000)-(0)-(2000)-(0)-(3000)-(0)-(4000)-(0)-(5000 A/m)-(0). Significant changes in the measured Ic-H (Hy,Hz) characteristics were observed above the certain value of Hz > 3000 A/m. We consider the shift of the measured Ic-H dependence in the Hz minus direction occurred because of the flux quanta were trapped in the sample superconducting niobium film after the Hz value had been added greater than 3000 A/m.

Modulation characteristics of DC Josephson current through Nb tunnel junction by applying external magnetic field in perpendicular direction.

Perpendicular magnetic field dependences of the Josephson current through tunnel junction were first measured. Niobium/aluminum-oxide/niobium (200/5/150 nm in thickness) superconducting tunnel junctions were fabricated by DC-magnetron apparatus with a load-lock chamber. Josephson current Ic through the superconducting junction is usually changed by the external magnetic field in one direction to check the barrier uniformity. To obtain more information of the barrier uniformity, we have changed the external magnetic field in two directions (Hx and Hy: parallel field to the junction plane) parallel to the junction plane. The shape of Ic-Hx curve and Ic-Hy curve were the Fraunhofer pattern in the Ic-Hx-Hy dependence of the junction with uniform barrier. This Ic-Hx-Hy dependence has no hysteresis. In this study, we have first applied the external magnetic field Hz perpendicular to the junction plane and have obtained Ic-Hz characteristics using three pairs of Helmholtz coils. In the case that the perpendicular field Hz < 2400 A/m, the Ic-Hz characteristics have a little hysteresis. The shape of Ic-Hz characteristics was similar to the Fraunhofer pattern. In the case that the perpendicular field Hz > 2400 A/m, the Ic-Hz characteristics have strong hysteresis. The Josephson current Ic always disappeared in the case that Hz > 7000 A/m. Two recovering methods of this current Ic were (a) alternating Hz field and (b) heating the sample to the room temperature and again cooling to the liquid He temperature.

Right-lateralized neural activity during inner speech repeated by cues.

Neural activity during inner speech of meaningless syllable sequences was measured with MEG and fMRI from eight right-handed subjects who executed a delayed-response task. An fMRI-constrained MEG multi-dipole analysis showed that active neural sources were detected at latencies of about 200-300 ms after cues near the posterior superior temporal sulcus and were more numerous in the right hemisphere than in the left hemisphere. Since the subjects were cued to repeat inner speech of meaningless sequences stored in verbal working memory, the activity in the right (language-nondominant) hemisphere suggested that the task required processing of more prosodic features such as pitch and rhythm than phonemic features.