Thin cylindrical dots with submicron diameter support vortex state in remanence [1,2]. In this paper, the dynamic properties of some dots with the above mentioned characteristics, have been sistematically investigated by Brillouin light scattering (BLS) from thermally excited spin waves. Array of cylindrical Ni81Fe19 (Permalloy) alloy dots with thickness of 50 nm and radius in the range between 0.1 and 0.5 ìm were prepared by means of electron-beam lithography and evaporation in ultrahigh vacuum using an electron beam gun. For each array the interdot separation is equal to the dot diameter. Fig.1 shows the BLS spectra for two arrays of cylindrical dots with radius of 0.1 and 0.5 micron and that of the continuous film. These spectra give evidence of a marked discretization of the spin wave mode: both the number and the frequency separation of the modes decreases as the dot radius is increased. In addition, the mode frequency increases for increasing the radius of the dots and tend toward the spin-wave frequency of the continuous film. These results are in qualitative agreement with the theoretical model proposed by Guslienko et al. [3] for tangentially magnetized cylindrical dots. However, this model does not reproduce the experimental frequencies in a quantitative way even if the agreement is better for larger dot radius for which the condition L<<R is better verified. Interestingly, we stress that the bulk standing mode, visible in the spectrum of the continuous film at about 18 GHz, does not appear in the spectra of the array of dots probably because of the presence of strong static demagnetizing field inside the dots. [1] T. Shinjo, T. Okuno, R. Hassdorf, K. Shigeto, and T. Ono, Science 289, 930 (2000). [2] G. Gubbiotti, G. Carlotti, R. Zivieri, F. Nizzoli, T. Okuno, T. Shinjo, IEEE Trans. on Magnetics, submitted. [3] K. Yu Guslienko and A. N. Slavin, J. Magn. Magn. Mater. 215, 576 (2000). -- Presentazione orale by R. Zivieri - Conferenza internazionale
Size-dependent spin wave frequency in submicron cylindrical dots -- Presentazione orale by R. Zivieri - Conferenza internazionale
ZIVIERI, Roberto;NIZZOLI, Fabrizio;
2002
Abstract
Thin cylindrical dots with submicron diameter support vortex state in remanence [1,2]. In this paper, the dynamic properties of some dots with the above mentioned characteristics, have been sistematically investigated by Brillouin light scattering (BLS) from thermally excited spin waves. Array of cylindrical Ni81Fe19 (Permalloy) alloy dots with thickness of 50 nm and radius in the range between 0.1 and 0.5 ìm were prepared by means of electron-beam lithography and evaporation in ultrahigh vacuum using an electron beam gun. For each array the interdot separation is equal to the dot diameter. Fig.1 shows the BLS spectra for two arrays of cylindrical dots with radius of 0.1 and 0.5 micron and that of the continuous film. These spectra give evidence of a marked discretization of the spin wave mode: both the number and the frequency separation of the modes decreases as the dot radius is increased. In addition, the mode frequency increases for increasing the radius of the dots and tend toward the spin-wave frequency of the continuous film. These results are in qualitative agreement with the theoretical model proposed by Guslienko et al. [3] for tangentially magnetized cylindrical dots. However, this model does not reproduce the experimental frequencies in a quantitative way even if the agreement is better for larger dot radius for which the condition L<I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
