Award type：Award from Japanese society, conference, symposium, etc.  Country：Japan

Country：Japan

Award type：Award from international society, conference, symposium, etc.  Country：Korea, Republic of

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)   Publisher：Physical Review B  

We report on spin ratchet currents driven by terahertz radiation electric fields in a Co/Pt magnetic metamaterial formed by triangle-shaped holes forming an antidot lattice and subjected to an external magnetic field applied perpendicularly to the metal film plane. We show that for a radiation wavelength substantially larger than the period of the antidots array, the radiation causes a polarization-independent spin-polarized ratchet current. The current is generated by the periodic asymmetric radiation intensity distribution caused by the near-field diffraction at the edges of the antidots, which induces spatially inhomogeneous periodic electron gas heating, and a phase-shifted periodic asymmetric electrostatic force. The developed microscopic theory shows that the magnetization of the Co/Pt film results in a spin ratchet current caused by both the anomalous Hall and the anomalous Nernst effects. Additionally, we observed a polarization-dependent trigonal spin photocurrent, which is caused by the scattering of electrons at the antidot boundaries resulting in a spin-polarized current due to the magnetization. Microscopic theory of these effects reveals that the trigonal photocurrent is generated at the boundaries of the triangle antidots, whereas the spin ratchet is generated due to the spatially periodic temperature gradient over the whole film. This difference causes substantially different hysteresis widths of these two currents.

DOI： 10.1103/PhysRevB.107.155419

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES  

DOI： 10.2322/tjsass.66.10

Web of Science

Scopus

CiNii Research

Language：English   Publisher：The Japan Society of Vacuum and Surface Science  

<p>Recently, various objects have become targets for sensing in order to realize an IoT society, and sensors are required higher sensitivity and miniaturization. In application of many automotive, aerospace, and industrial fields, there is a high need for compact sensors to measure mechanical quantities such as strain, stress. Strain gauge are intended to measure the magnitude and direction of the strain and the magnetostrictive effect in ferromagnetic films can be applied to strain detection. In this research, a GIG (Granular in Gap) structure [1] is used for a new strain gauge. It has a structure in which a granular film is sandwiched between soft magnetic yokes. When the strain is applied to the device, the change of strain is detected as a resistance change in the granular film. Co-AlO and amorphous(a)-FeSiBNb were employed as the granular film and the soft magnetic yoke of the strain gauge. The thickness of Co-AlO film and a-FeSiBNb yoke was 300 nm. The structure of the strain gauge is indicated in the inset of Figure 1. The gap length was estimated to be approximately 4 µm. An AC voltage at 80Hz supplied from a lock-in-amplifier (LIA) is applied to the series circuit of the gauge and a variable resistor. When the strain is applied to the gauge, the strain is detected as a voltage of the gauge by LIA. The MR ratio of the Co-AlO granular film before processing into a GIG element was about 6%. The magnetostriction constant of a-FeSiBNb yoke was 30.4ppm. A magnetic field of 5 Oe must be applied in direction of H⊥gap in order to align the magnetic moments of yokes. The granular film becomes a low resistance state due to a magnetic field appeared in the gap yielded by magnetic poles at the edge of yokes. When the strain is applied in direction of H//gap, the magnetic moments of yokes change its direction, increasing the resistance of granular film owing to the decrease of the magnetic field in the gap. The dependence of output voltage on the applied strain ε is shown in Fig.1. The blue circles are the result of increasing strain, and the red circles are the result of decreasing strain. The output voltage became large with increasing strain, and gradually almost constant because the magnetic moments of yokes saturated in direction of H//gap. This indicates that the strain up to about 6.0 × 10^-5 can be detected. The gauge factor estimated was approximately 50, larger than that of a typical metal strain gauge. Reference [1] N. Kobayashi et al., J. Magn. Magn. Mater. 188. 30 (1998).</p>

DOI： 10.14886/jvss.2023.0_1p34

CiNii Research

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.35848/1347-4065/abd6e0

Event date： 2023.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya University   Country：Japan  

Application no：特開2014-116510  Date applied：2014