Magnetic Resonance Studies of the Origin of Ferromagnetism in Ga 1-x Mn x As
O.M. Fedorych a , Z. Wilamowski a , M. Potemski b , M. Byszewski b and J. Sadowski c,a
a Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warsaw, Poland
b Grenoble High Magnetic Field Laboratory, MPI/CNRS 380-42 Grenoble, France
c Niels Bohr Institute, Copenhagen University, 2100 Copenhagen, Denmark
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Different types of magnetic resonance observed in Ga 1-x Mn x As reflect three different magnetic phases: para-, ferro-, and ferrimagnetic. Ferromagnet is characterized by single isotropic resonance line. A complex spectrum in ferrimagnet can be described by g factor equal to 1.44 and a sum of an axial and cubic anisotropy field. The axial field is by an order of magnitude greater than the cubic one. The complex structure of ferrimagnetic resonance is attributed to spin-wave resonance. Quantitative analysis of the dispersion of spin wave shows that the range of exchange coupling is very long, of the order of 25 nm, while spin-wave stiffness and the total exchange field are very small. The exchange field as evaluated from spin wave is by two orders of magnitude smaller than the Zener field corresponding to the critical temperature.
DOI: 10.12693/APhysPolA.103.607
PACS numbers: 71.55.Eq, 76.30.Fc, 75.50.Pp, 75.30.Gw