The magnetization dynamics of a two-sublattice ferrimagnet near the angular momentum compensation point

The high-frequency properties of a two-sublattice ferrimagnet at temperatures near the angular momentum compensation point T_L are studied. The diagram technique for spin operators, as well as the analytical expressions applicable in the total temperature interval of magnetic ordering are used. It is shown that near T_L the longitudinal magnetic fluctuations substantially affect the resonance properties of the magnet, so that temperature behaviors of in-phase and opposite-phase precessions of sublattice magnetizations are different. With approaching T_L the frequency of the in-phase precession increases simultaneously with a significant increase of the line width, while the frequency of the opposite-phase oscillation substantially decreases, so that the both types of oscillations are equal. The results obtained are important for understanding of microscopic mechanisms of magnetization reverse by ultrashort laser pulses in rare-earth ferrimagnets.

PACS: 75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.);
PACS: 75.50.Gg Ferrimagnetics;
PACS: 76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance.

Key words: two-sublattice ferrimagnet, magnetization dynamics at finite temperature, temperature magnetization fluctuations, temperature of sublattices angular momentum compensation.

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