Kalita V. Magnetoelasticity and anisotropy phenomena in magnetic properties of ferro- and antiferromagnetics

The dissertation is devoted to description of magnetostriction and anisotropy impact on magnetic properties of high symmetric ferro- and antiferromagnetics with the property of multiple spatial degeneration of the order parameter. Easy plane ferro- and antiferromagnetics have been considered. It is shown that in easy plane antiferromagnetics of iron group dihalides multidomain state is of magnetoelastic nature when thermodynamically equilibrium multidomain state is caused by coordination of domain striction with defects' elastic fields. In ferro- and antiferromagnetics with S=1 and with single-ion easy plane anisotropy comparable with an exchange interaction, spontaneous magnetic ordering and ordering due to magnetic field or hydrostatic pressure occurs as magnetic phase transitions of displacement type, when order parameter is spin polarization of single-ion states.