Implications of a temperature-dependent magnetic anisotropy for superparamagnetic switching

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

卷:447

Article

Stier, Martin¹  Neumann, Alexander²  Philippi-Kobs, Andre^2,3  Oepen, Hans Peter²  Thorwart, Michael¹ 

[1] Univ Hamburg, Inst Theoret Phys 1, Jungiusstr 9, D-20355 Hamburg, Germany

[2] Univ Hamburg, Inst Nanostruktur & Festkorperphys, Jungiusstr 11, D-20355 Hamburg, Germany

[3] Deutsch Elektronen Synchrotron DESY, Notkestr 85, D-22607 Hamburg, Germany

关键词: Superparamagnetism;    Arrhenius law;    Neel-Brown theory;    Attempt frequency;   

DOI  :  10.1016/j.jmmm.2017.09.068

来源: Elsevier

【 摘 要 】

The macroscopic magnetic moment of a superparamagnetic system has to overcome an energy barrier in order to switch its direction. This barrier is formed by magnetic anisotropics in the material and may be surmounted typically after 10(9) -10(12) attempts per second by thermal fluctuations. In a first step, the associated switching rate may be described by a Neel-Brown-Arrhenius law, in which the energy barrier is assumed as constant for a given temperature. Yet, magnetic anisotropics in general depend on temperature themselves which is known to modify the Neel-Brown-Arrhenius law. We illustrate quantitatively the implications of a temperature-dependent anisotropy on the switching rate and in particular for the interpretation of the prefactor as an attempt frequency. In particular, we show that realistic numbers for the attempt frequency are obtained when the temperature dependence ofthe anisotropy is taken into account. (c) 2017 Elsevier B.V. All rights reserved.

【 授权许可】

Free