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ATTENTION !!! CHANGEMENT D’HORAIRE - Thermal and dynamical properties of the permanent magnet Nd2Fe14B at finite temperatures

Vendredi 14 septembre 14:00 - Duree : 1 heure
Lieu : Salle « Remy Lemaire » (K223) de l’Institut Néel – au n°25 de la rue des martyrs, Grenoble.

Orateur : Seiji MIYASHITA ( University of Tokyo, Bunkyo-Ku, Tokyo and the Elements Strategy Initiative Center for Magnetic Materials, NIMS, Tsukuba, 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 constant s[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 reorientation transition[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.

All people who do not have a CNRS badge must inform us of their arrival nora.dempsey@neel.cnrs.fr

Contact : nora.dempsey@neel.cnrs.fr

Discipline évènement : (Physique)
Entité organisatrice : (Institut Néel / QUEST)
Nature évènement : (Séminaire)
Site de l'évènement : Polygone scientifique

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