Vendredi 14 septembre à 14h,
Salle Remy Lemaire, K223

Orateur : Seiji Miyashita, University of Tokyo

Thermal and dynamical properties of the permanent magnet Nd2Fe14B at finite temperatures

Seiji Miyashitaab, Masamichi Nishinobc, Yuta Togab, Taichi Hinokiharaab, Takashi Miyakebd, Satoshi Hirosawab, Akimasa Sakumabe

aDepartment of Physics, Graduate School of Science, The University of Tokyo, Bunkyo-Ku, 113-0033 Tokyo, Japan
bElements Strategy Initiative Center for Magnetic Materials (ESICMM), National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan
cInternational Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
dCD-FMat, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan
eDepartment of Applied Physics, Tohoku University, Sendai 980-8579, Japan

The thermal and dynamical properties of Nd2Fe14B at finite temperatures are studied with an atomic model Hamiltonian with microscopic parameters [1,2]. We have studied temperature dependences of the magnetization including the reorientation transition, anisotropy constants [3], and also domain wall shape [4], etc.
The atom-specific information has been also obtained. E.g., it was found that the magnetic moment of Nd decreases faster than that of Fe with increasing temperature[3], and also dependence of the exchange stiffness constant on the lattice axes has been obtained[4,5]. Effects of the dipole-dipole interaction are studied introducing a new numerical algorithm[6], where the role of Fe ion for the coercive force at high temperature was pointed out, and also various non-uniform magnetic patterns (e.g., maze pattern) are presented.
In addition to the static thermal properties, dynamics of the magnetization in unfavorable magnetic field has been studied by stochastic LLG equation [4,7,8] and also by Monte Carlo methods. Temperature dependence of spectrum of the ferromagnetic resonance is discussed in the relation to the reorientationtransition[9]. By making use of LLG equation and also by a MC method for free energy barrier, temperature dependence of the coercive field is discussed.

[1] S. Hirosawa, M. Nishino, S. Miyashita, Adv. Nat. Sci. : Nanosci. Nanotechnol. 8 (2017) 013002.
[2] S. Miyashita, M. Nishino, Y. Toga, T. Hinokihara, T. Miyake, S. Hirosawa and A. Sakuma, Scripta Materialia, in press.
[3] Y. Toga, M. Matsumoto, S. Miyashita, H. Akai, S. Doi, T. Miyake, and A. Sakuma : Phys. Rev. B 94, 174433 (2016). & Phys. Rev. B 94, 219901 (2016).
[4] M. Nishino, Y. Toga, S. M., H. Akai, A. Sakuma, and S. Hirosawa, Phys. Rev. B 95, 094429 (2017).
[5] Y. Toga, M. Nishino, S. Miyashita, T. Miyake, and A. Sakuma, in preparation (Phys. Rev. B).
[6] T. Hinokihara, M. Nishino, Y. Toga, and S. Miyashita, Phys. Rev. B97, 104427 (2018).
[7] M. Nishino and S. Miyashita, Phys. Rev. B91, 134411(1-13) (2015).
[8] S. Mohakud, S. Andraus, M. Nishino, A. Sakuma, S. M., Phys. Rev. B 94, 054430 (2016).
[9] M. Nishino and S. Miyashita, in preparation.

Dans la même rubrique

© Institut Néel 2012 l Webdesign l Propulsé par spip l Dernière mise à jour : mercredi 10 juin 2020 l