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MA: Fachverband Magnetismus

MA 46: Magnetic Measurement Methods

MA 46.9: Talk

Thursday, March 10, 2016, 17:45–18:00, H33

The Magnonic Heat Capacity measured by Ferromagnetic Resonance in Metastable Magnetic States — •Benjamin Zingsem, Sabrina Masur, Paul Wendtland, Michael Winklhofer, Markus Ernst Gruner, Ruslan Salikhov, Florian M. Römer, Ralf Meckenstock, and Michael Farle — Faculty of Physics and Center for Nanointegration (CENIDE), University Duisburg-Essen, 47057 Duisburg, Germany

We report on ferromagnetic resonance (FMR) in metastable states and show experimentally that resonant absorption in such magnetic states can be achieved via unconventional angular dependent FMR measurements. Calculations of such an unconventional FMR are compared to experimental results obtained from a 10 nm Fe thin film measured in X-band at temperatures ranging from 50 K to 300 K. In this comparison we find a difference between the critical field and angle configurations at which the metastable states spontaneously decay. We interpret this difference in terms of thermal fluctuations in the real physical system. By applying spin wave theory to calculate the magnonic heat capacity [1] we show that the temperature derivative of the Zeeman energy at these critical points in the experiment is proportional to the magnonic heat capacity, while the difference in the applied field strength at a given angle is given by the thermal fluctuation field [2]. [1] S. M. Rezende et al. Phys. Rev. B, 91 (2015) 104416 [2] S. Bance et al. Applied Physics Letters, 105 (2014)