Current-induced enhancement of magnetic anisotropy in spin-charge-coupled multiferroic YbFeO

Yoshii, Kenji; Matsumura, Daiju; Saito, Hiroyuki; Kambe, Takashi*; Fukunaga, Mamoru*; Muraoka, Yuji*; Ikeda, Naoshi*; Mori, Shigeo*

Journal of the Physical Society of Japan, 83(6), p.063708_1 - 063708_4, 2014/06

https://doi.org/10.7566/JPSJ.83.063708

We report the change of magnetic properties of multiferroic YbFeO, caused by cooling in the presence of an electrical current. The magnetization measured after the cooling becomes smaller by about 10-20% than that after cooling without a current. The current also affects the magnetic anisotropy below about 100 K; the magnetic coercivity is increased by about 10-20%. These phenomena may arise from a coexistence of ferromagnetic and antiferromagnetic domains, or a disturbance in the formation of charge-ordered domains. From the applied viewpoint, the enhancement of anisotropy by an electrical current offers a method for stabilizing magnetization other than the well-known method, i.e., exchange bias.

Spin chirality and electric polarization in multiferroic compounds RMnO ( = Ho, Er)

Wakimoto, Shuichi; Kimura, Hiroyuki*; Fukunaga, Mamoru*; Nishihata, Keisuke*; Takeda, Masayasu; Kakurai, Kazuhisa; Noda, Yukio*; Tokura, Yoshinori*

Physica B; Condensed Matter, 404(17), p.2513 - 2516, 2009/09

https://doi.org/10.1016/j.physb.2009.06.012

Magnetic-field-induced magnetic phase transitions associated with ferroelectricity in multiferroic ErMnO

Kimura, Hiroyuki*; Wakimoto, Shuichi; Fukunaga, Mamoru*; Noda, Yukio*; Kaneko, Koji; Metoki, Naoto; Kakurai, Kazuhisa; Kay, Kohn*

Journal of the Physical Society of Japan, 78(3), p.034718_1 - 034718_5, 2009/03

https://doi.org/10.1143/JPSJ.78.034718

Study on microbial influence assessment in geological disposal

Fukunaga, Sakae*; Nakayama, Mamoru*; Jintoku, Takashi*; *; Kudo, Akira*

JNC TJ8400 2002-036, 186 Pages, 2002/02

JNC-TJ8400-2002-036.pdf:1.34MB

We conducted the following four investigations concerned with microbial influence in geological disposal facilities. (1)Improvement of the FEP dictionary and investigation on chemical evolution of nitrate by microbes. (2)Experimental estimation of microbial mobility in compacted Na bentonite saturated by synthetic seawater with 30wt% silica sand and Ca bentonite with 30wt% silica sand. (Both dry densities are 1.6 g/cm.) (3)Habitation of microbes in Na rich bentonite deposit and Ca rich one. (4)Interaction between SRB (sulfate reducing bacteria) and Np in a reducing environment at Eh=-85mV. As the result, it was revealed that (1)microbial activity in near field rock and microbial denitrification of nitrate under the existence of electron donor are important, (2)microbes didn't move in Na bentonite in 3 weeks and moved to the distance of 20mm in Ca bentonite, and (3)microoragnisms existed at the inside of the deposits. (4)The difference between distribution coefficient of Eh=-85mV and Eh=-500mV was evaluated.

Linear relation between magnetic chirality and spontaneous polarizatin in multiferroic MnO (=Ho, Er)

Wakimoto, Shuichi; Kimura, Hiroyuki*; Nishihata, Keisuke*; Fukunaga, Mamoru*; Takeda, Masayasu; Kakurai, Kazuhisa; Noda, Yukio*; Tokura, Yoshinori*

no journal, , 

Polarized neutron scattering experiments have been performed on multiferroic materials MnO (Ho, Er) under electric fields to study the direct relation between the electric polarization and the magnetic chiral structure of Mn spins. It is found that the magnetic chirality is proportional to the polarization, consisntent with the inverse-DM model.

Magnetic chirality and electric polarization in multiferroic MnO

Wakimoto, Shuichi; Kimura, Hiroyuki*; Fukunaga, Mamoru*; Nishihata, Keisuke*; Takeda, Masayasu; Kakurai, Kazuhisa; Noda, Yukio*; Tokura, Yoshinori*

no journal, , 

Polarized neutron diffraction experiments have been performed on multiferroic materials MnO (Ho, Er) under electric fields in the ferroelectric commensurate (CM) and the low-temperature incommensurate (LT-ICM) phases. It is found that the magnetic chirality is proportional to the electric polarization and magnetic chirality can be switched by the polarity of the electric polarization in both the CM and LT-ICM phases. However, upon the transition from the CM to LT-ICM phase, the reduction of the electric polarization is not accompanied by any reduction of the magnetic chirality, implying that the CM and LT-ICM phases contain different mechanisms of the magnetoelectric coupling.

Spin chirality and electric polarization in Ga-doped YMn(MnGa)O

Wakimoto, Shuichi; Kakurai, Kazuhisa; Sakamoto, Yuma*; Fukunaga, Mamoru*; Kimura, Hiroyuki*; Noda, Yukio*

no journal, , 

no abstracts in English

Magnetic chirality and electric polarization in multiferroic YMnO

Wakimoto, Shuichi; Kimura, Hiroyuki*; Fukunaga, Mamoru*; Sakamoto, Yuma*; Noda, Yukio*; Kakurai, Kazuhisa

no journal, , 

A Role of the magnetic chirality in polarization flip in YMnO

Wakimoto, Shuichi; Kimura, Hiroyuki*; Fukunaga, Mamoru*; Sakamoto, Yuma*; Takeda, Masayasu; Kakurai, Kazuhisa; Noda, Yukio*

no journal, ,