Author:
Kokorina E. E.,Medvedev M. V.
Abstract
Abstract
It is shown that the temperature transition from a disordered paramagnetic state to the ground ferromagnetic state in a magnet with sufficiently strong biquadratic exchange interaction (compared to bilinear exchange) and spin S > 1 passes through an intermediate magnetically ordered phase (uniaxial quadrupole ordering). For a magnet with spin S = 3/2, a phase diagram of magnetic states in the region of large values of the biquadratic exchange is constructed in the mean-field approximation and the influence of the sequence of two phase transitions (paramagnetic state−quadrupole state and quadrupole state–ferromagnetic state) on the temperature behavior of the magnetic heat capacity and the initial magnetic susceptibility is investigated.