Zavrazhnaja E. Influence of a magnetic field on conditions antiferromagnetic with prevailing interaction Dzyaloshinsky's

The thesis presents a phase diagram for easy-axis tetragonal antiferromagnetic with dominant Dzyaloshinski interaction in Hz - Hy. In the diagram the second-order transition lines between the angular phase and the phase with the vector of antiferromagnetism l perpendicular to easy-magnetization axis (EMA), begin and finish in the fields of spin-flip transition, i.e. in the exchange field. Each line has two tricritical points where the transition to the first-order phase line occurs. A critical angle between the sense of magnetic field and basal plane where the above process takes place was determined. The value of the angle and tricritical point coordinates in the Hz- Hy or Hz- Hx phase diagram depend on temperature. The thesis also presents complete H-T phase diagram of the antiferromagnetic cobalt fluoride when the external magnetic field H is perpendicular to EMA. Based on this diagram Hz - Hy phase diagram was plotted. Investigation was carried out into the magnetic subsystem of cobalt fluoridein strong magnetic field with arbitrary direction in space. It was proved that the transition of the vector l to the basal plane proceeds only if the magnetic field is perpendicular to EMA. The case when magnetic field is directed along the [110] axis was thoroughly studied. Experimental methods of magnetic phase diagram plotting using dielectric resonance are described. To this end, the behavior of components of the statistic magnetic susceptibility tensor in the vicinity of the tricritical points in the lines of the first- and second-order phase transitions was determined.