2015/06/24 by Martin Stier, Alexander Neumann, Stier, Martin +7
Physics and Astronomy · Biochemistry, Genetics and Molecular Biology · #Scientific Research and Discoveries #Geomagnetism and Paleomagnetism Studies #Magnetic properties of thin films
paper · pdf · doi:10.48550/arxiv.1506.07333
The macroscopic magnetic moment of a superparamagnetic system has to overcome\nan energy barrier in order to switch its direction. This barrier is formed by\nmagnetic anisotropies in the material and may be surmounted typically after\n109 to 1012 attempts per second by thermal fluctuations. In a first step, the\nassociated switching rate may be described by a Neel-Brown-Arrhenius law, in\nwhich the energy barrier is assumed as constant or a given temperature. Yet,\nmagnetic anisotropies in general depend on temperature themselves which is\nknown to modify the Neel-Brown-Arrhenius law. We illustrate quantitatively the\nimplications of a temperature-dependent anisotropy on the switching rate and in\nparticular for the interpretation of the prefactor as an attempt frequency. In\nparticular, we show that realistic numbers for the attempt frequency are\nobtained when the temperature dependence of the anisotropy is taken into\naccount.\n