References of "Viswanath, R. N."
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See detailA neutron-scattering investigation of the magnetic structure and magnetic excitations in nanocrystalline Tb
Vecchini, C.; Moze, O.; Hoser, A. et al

in Journal of Applied Physics (2006), 99(8), 5021-5023

The magnetic structure and magnetic excitations in nanocrystalline Tb have been investigated by neutron diffraction and neutron spectroscopy. This is a report on the long-range magnetic order and the ... [more ▼]

The magnetic structure and magnetic excitations in nanocrystalline Tb have been investigated by neutron diffraction and neutron spectroscopy. This is a report on the long-range magnetic order and the magnetic excitations in a nanocrystalline elemental rare earth. Refinement of the neutron-diffraction data reveals an “average” magnetic structure of each crystallite which contains a significant out-of-plane component to the magnetic moment as well as a suppression of the high-temperature antiferromagnetic phase observed for coarse-grained Tb. The inelastic-neutron-scattering measurements reveal the presence of a magnetic excitation of approximately 10 meV at 2.5 K. The excitation energy decreases with increasing temperature. The origins of this excitation are discussed with particular reference to the magnetic modes at the zone center observed for single-crystal Tb. [less ▲]

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See detailCharacteristic magnetic length-scales in Vitroperm—Combining Kerr microscopy and small-angle neutron scattering
Grob, A.; Saranu, S.; Herr, U. et al

in Physica Status Solidi A. Applied Research (2004), 201

We present a study of the magnetic-field dependence of the magnetic microstructure of the nanocrystalline soft magnet Vitroperm (Fe73Si16B7Nb3Cu1), which was treated so as to exhibit a macroscopic ... [more ▼]

We present a study of the magnetic-field dependence of the magnetic microstructure of the nanocrystalline soft magnet Vitroperm (Fe73Si16B7Nb3Cu1), which was treated so as to exhibit a macroscopic magnetic anisotropy. The samples were analysed using Kerr microscopy and small-angle neutron scattering (SANS). As the applied magnetic field is decreased starting from saturation, we find that two processes occur independently: the formation of a domain structure with the net magnetisation of the domains aligned along the macroscopic easy axis and the increase in magnitude of static, nanometer-scale fluctuations of the spin orientation. The domain structure observations from Kerr microscopy are in excellent agreement with the results of the SANS experiments. [less ▲]

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See detailDomain formation and long-range spin disorder in Vitroperm
Michels, Andreas UL; Viswanath, R. N.; Weissmüller, J.

in Europhysics Letters (2003), 64

We present a study of the magnetic-field dependence of the small-angle neutron scattering of the nanocrystalline soft magnet Vitroperm (Fe73Si16B7Nb3Cu1), which was treated so as to exhibit a macroscopic ... [more ▼]

We present a study of the magnetic-field dependence of the small-angle neutron scattering of the nanocrystalline soft magnet Vitroperm (Fe73Si16B7Nb3Cu1), which was treated so as to exhibit a macroscopic magnetic anisotropy. We show how the field dependences of i) the radial average of the scattering cross-section dΣ/dΩ and ii) the variation of dΣ/dΩ as a function of the orientation of the scattering vector can be analysed to supply separately information on the orientation of the net magnetisation of the domains and on the internal spin disorder within the domains. As the applied magnetic field is decreased starting from saturation, we find that two processes occur independently: the formation of a domain structure with the net magnetisation of the domains aligned along the macroscopic easy axis and the increase in magnitude of static, nanometer-scale fluctuations of the spin orientation. [less ▲]

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See detailRange of magnetic correlations in nanocrystalline soft magnets
Michels, Andreas UL; Viswanath, R. N.; Barker, J. G. et al

in Physical Review Letters (2003), 91

We have obtained the magnetic field dependence of static ferromagnetic correlations in nanocrystalline electrodeposited Co and Ni by means of the correlation function of the spin misalignment, determined ... [more ▼]

We have obtained the magnetic field dependence of static ferromagnetic correlations in nanocrystalline electrodeposited Co and Ni by means of the correlation function of the spin misalignment, determined from small-angle neutron scattering data. The approach yields a correlation length lC, which is a measure for the spatial extent of inhomogeneities in the magnetization distribution. The correlation length depends strongly on the applied magnetic field with values ranging from 94 nm in nanocrystalline Co at low fields to about 15 nm at saturation. The results for lC indicate that in Co the main source of nonuniformity in the spin system is the anisotropy field of each individual crystallite, whereas in nanocrystalline Ni the main sources of spin disorder originate from twin faults or from the defect cores of grain boundaries. [less ▲]

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