Magnetooptisches NanoMagnetometer
Final Report Abstract
The main part of the nanomagnetometer is the scanning Faraday/Kerr magneto-optical microscope, based on a fs-laser. It allows one to investigate magnetic dynamics with combined time-domain and spatial resolution. Since the device is complementary to the Brillouin light scattering technique which allows studies with frequency and wavevector resolution, in most of the studies both techniques were applied to fully characterize dynamics of the studied systems. Moreover, the probing fs-laser pulses was also synchronizing with an external microwave-frequency sinusoidal signal. In this setup by tuning the frequency of the microwave signal to the frequencies of the magnetic eigenmodes of the system, one may directly image these eigenmodes in real space with a phase-resolution. The device was used in different international and German research projects as listed below: 1. Microwave Amplification by Spin Transfer Emission Radiation (MASTER) FP7-NMP-2007-SMALL-212257 (Germany, France, Italy, Great Britain, Poland) 2. Nanowire nased microwave emitters for use in monolithic integrated circuits ERA NanoSci+ De-639/7-1 (Germany, Ireland, Spain) 3. Study of Bose-Einstein condensate of magnons by means of fs-laser Faraday magnetometry De-639/9-1 (Germany, Netherlands) 4. Nonlinear spin waves in non-uniform potentials De-639/6-1 5. Nonlinear nanooptics with spin waves DE 1511/1-1 Three main scientific topics of these studies can be identified: 1. Investigation of magnetostatic spin-wave modes in macroscopic confined systems. Taking advantage of high spatial resolution of the optical technique, we were able to image and to study high-order spin-wave modes yttrium iron garnet disk. It was shown that widely used factorization of twodimensional modes as a combination of two one-dimensional modes cannot be applied due to the non-local and anisotropic nature of the magnetic dipole interaction dominating in macroscopic systems. 2. Investigation of magnetostatic spin-wave modes in microscopic confined systems. Microscopic confined systems build a basis for numerous spintronic devices as spin-torque- and spin-Hall nano-oscillators, where non-linear effects play a decisive role. Combining the fs-laser magnetometry technique with the micro-BLS spectroscopy we have studied of eigenmodes in these systems, and demonstrated, in particular, the importance of non-uniform magnetic fields as well of intrinsic nonlinearity of magnetic precession for the above phenomena. 3. Study of Bose-Einstein condensation (BEC) of magnons BLS is up to now the main experimental technique for investigation of BEC. However, due to its limited frequency resolution the BLS technique cannot provide a correct data on the degree of the temporal coherence (frequency linewidth) of the Bose-Einstein condensate. A combined heterodyne scheme based on the fs-laser magnetometry is currently used to determine the linewidth with the accuracy below 1 MHz.
Publications
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“Nonlinear Hybridization of the Fundamental Eigenmodes of Microscopic Ferromagnetic Ellipses”. Phys. Rev. Lett. 104 (2010) 217203
V.E. Demidov, M. Buchmeier, K. Rott, P. Krzysteczko, J. Münchenberger, G. Reiss, and S.O. Demokritov
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“Control of magnetic fluctuations by spin current”. Phys. Rev. Lett. 107 (2011) 107204
V. E. Demidov, S. Urazhdin, E. R. J. Edwards, M. D. Stiles, R. D. McMichael, S. O. Demokritov
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“Parametric excitation of magnetization oscillation controlled by pure spin current”. Phys. Rev. B 86 (2012) 134420
E.R.J. Edwards, H. Ulrichs, V.E. Demidov, S.O. Demokritov, and S. Urazhdin
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“Magnetostatic spin-wave modes of an in-plane magnetized garnet-film disk”. J. Appl. Phys. 113, 103901 (2013)
E.R.J. Edwards, M. Buchmeier, V.E. Demidov, and S.O. Demokritov
