Experimental and theoretical studies of the dynamic magnetization in swept
magnetic fields of the orthorhombic SrY2βO4β single-crystals doped with the
Dy3+ Kramers ions (0.01 and 0.5 at.%) with natural abundances of even and
odd Dy isotopes are presented. Impurity ions substitute for Y3+ ions at
two nonequivalent crystallographic sites with the same local Csβ symmetry but
strongly different crystal fields. Well pronounced double-loop hysteresis is
observed at temperatures 2, 4, 5 and 6 K for sweeping rates of 5 and 1 mT/s.
The microscopic model of spectral, magnetic and kinetic properties of Dy3+
ions is developed based on the results of EPR, site selective optical spectra
and magnetic relaxation measurements. The derived approach to the dynamic
magnetization in the sweeping field based on the numerical solution of
generalized master equations with time-dependent transition probabilities
induced by the electron-phonon interaction, quantum tunneling and
cross-relaxation allowed us to reproduce successfully the evolution of the
hysteresis loop shape with temperature, sweeping rate and concentration of
paramagnetic ions.Comment: 11 pages, 6 figures, 2 tables, 52 reference