EuTiO3: The low-energy electronic structure of Eu2+ from the specific heat

We present the low-energy electronic structure originating from the S7/28 ground multiplet of the Eu2+ ions derived from theoretical description of the temperature dependence of the specific heat at low temperatures, including the λ-type peak at TN, both at zero field and in external magnetic fields. The derived energy states are the physical reality - they can be probed by different techniques and on this basis results of different theoretical models can be compared. Our atomic-like approach consistently explains zero-temperature properties and thermodynamics. We separate the derived molecular field at T = 0 K of 2.73 T for contributions coming from antiferro- and ferromagnetic interactions and derived exchange constants J1 = −16.6 mK (AF) and J2 = +35.3 mK (F).