The properties of lattice, electronic and magnetic subsystems of erbium tetraboride based on calorimetric data at temperatures of 2―300 K

The temperature dependence of heat capacity С р (Т ) of an erbium tetraboride sample, synthesised by the borothermal reduction of metal from oxide in a vacuum, is researched by the absolute adiabatic calorimetry method. The transition of the tetraboride into an antiferromagnetic state at TN = 15.1 K is revealed on the С р (Т ) curve by a sharp maximum. The values of ErB4 heat capacity are presented as the sum of electronic С е (Т ), magnetic С m(Т ), and lattice С lat(Т ) components, as well as Schottky contribution С Sch(Т ). The characteristics of these components are defined: the electronic heat capacity coefficient, parameter of interaction in the magnetic subsystem, entropy and enthalpy of magnetic transformation, splitting scheme of Er3+ ion level, and the residual entropy of the magnetic subsystem at absolute zero, conditioned by the lattice frustration of erbium tetraboride.