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

• The specific heat of erbium tetraboride at 2–300 K was experimentally investigated.
• The nature of the ground state is established.
• The Schottky contribution to the specific heat of tetraboride is identified.
• The residual entropy of the of atomic magnetic moments of Er3+ system was detected.

The temperature dependence of heat capacity Ср(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 Ср(Т) curve by a sharp maximum. The values of ErB4 heat capacity are presented as the sum of electronic Се(Т), magnetic Сm(Т), and lattice Сlat(Т) components, as well as Schottky contribution СSch(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.