Zeeman effect and energy level crossing in strong magnetic field in rare-earth compounds RBa$_2$Cu$_3$O$_{7-\delta}$, R = Dy, Ho, Er, Tm

The authors have calculated the Zeeman effect, magnetization and magnetic susceptibility in isothermal and adiabatic conditions for compounds RBa$_2$Cu$_3$O$_{7-\delta}$ in the tetragonal ($\delta\approx1.0$) and orthorhombic ($\delta\approx0$) phases with Dy, Ho, Er, and Tm ions. The effects of interaction between the energy levels of rare-earth ions (crossover) have been shown to exist for all compounds studied. The averaging of magnetic characteristics for polycrystalline specimens has made possible the determination of conditions under which the above effects can be observed experimentally on polycrystals.