Anomalous temperature dependence of current-induced torques in CoFeB/MgO heterostructures with Ta-based underlayers

Kim, J.*; Sinha, J.*; Mitani, Seiji*; Hayashi, Masamitsu*; Takahashi, Saburo*; Maekawa, Sadamichi; Yamanouchi, Michihiko*; Ohno, Hideo*

Physical Review B, 89(17), p.174424_1 - 174424_8, 2014/05

https://doi.org/10.1103/PhysRevB.89.174424

We have studied the underlayer thickness and temperature dependencies of the current-induced effective field in CoFeB/MgO heterostructures with Ta-based underlayers. The underlayer thickness at which the effective field saturates is found to be different between the two orthogonal components of the effective field; i.e., the dampinglike term tends to saturate at a smaller underlayer thickness than the fieldlike term. For large underlayer thickness films in which the effective field saturates, we find that the measurement temperature significantly influences the size of the effective field. A striking difference is found in the temperature dependence of the two components: the dampinglike term decreases whereas the fieldlike term increases with increasing temperature. Using a simple spin diffusion-spin transfer model, we find that all of these results can be accounted for provided the real and imaginary parts of an effective spin mixing conductance are negative. These results imply that either spin transport in this system is different from conventional metallic interfaces or effects other than spin diffusion into the magnetic layer need to be taken into account in order to model the system accurately.

Time-domain observation of the spinmotive force in permalloy nanowires

Hayashi, Masamitsu*; Ieda, Junichi; Yamane, Yuta; Oe, Junichiro*; Takahashi, Yukiko*; Mitani, Seiji*; Maekawa, Sadamichi

Physical Review Letters, 108(14), p.147202_1 - 147202_5, 2012/04

https://doi.org/10.1103/PhysRevLett.108.147202

Spinmotive force associated with a moving domain wall is observed directly in permalloy nanowires using real time voltage measurements with proper subtraction of the electromotive force. Whereas the wall velocity exhibits nonlinear dependence on a magnetic field, the generated voltage increases linearly with the field. We show that the sign of the voltage reverses when the wall propagation direction is altered. Numerical simulations explain quantitatively these features of spinmotive force and indicate that the spinmotive force scales with the field even in a field range where the wall motion is no longer associated with periodic structure transformation.

Performance test results of helium gas circulator of mock-up test facility with full-scale reaction tube for HTTR hydrogen production system (Contract research)

Shimizu, Akira; Kato, Michio; Hayashi, Koji; Fujisaki, Katsuo; Aita, Hideki; Takeda, Tetsuaki; Nishihara, Tetsuo; Katanishi, Shoji; Takada, Shoji; Inaba, Yoshitomo; et al.

JAERI-Tech 2003-033, 105 Pages, 2003/03

JAERI-Tech-2003-033.pdf:8.35MB

no abstracts in English

Direct observation of higher order atomistic structure in TiNiFe at lower temperature phase

Hu, W.; Hayashi, Koichi*; Happo, Naohisa*; Hosokawa, Shinya*; Terai, Tomoyuki*; Fukuda, Takashi*; Kakeshita, Tomoyuki*; Takahashi, Masamitsu

no journal, , 

Precursor phenomena of martensitic transformation in Fe-doped Ti-Ni alloys studied by X-ray fluorescence holography

Hu, W.; Hayashi, Koichi*; Happo, Naohisa*; Terai, Tomoyuki*; Fukuda, Takashi*; Kakeshita, Tomoyuki*; Takahashi, Masamitsu

no journal, , 

3D local structure analysis of relaxor ferroelectrics Pb(MgNb)O by X-ray fluorescence holography

Hu, W.; Hayashi, Koichi*; Happo, Naohisa*; Owada, Kenji; Chen, J.*; Ye, Z.-G*; Hosokawa, Shinya*; Takahashi, Masamitsu

no journal, ,