We have investigated the magnetocaloric effect in single and polycrystalline samples of quantum paraelectric EuTiO 3 by magnetization and heat capacity measurements. Single crystalline EuTiO 3 shows antiferromagnetic ordering due to Eu 2+ magnetic moments below T N = 5.6 K. This compound shows a giant magnetocaloric effect around its Néel temperature. The isothermal magnetic entropy change is 49 J kg −1 K −1 , the adiabatic temperature change is 21 K, and the refrigeration capacity is 500 J kg −1 for a field change of 7 T at T N . The single crystal and polycrystalline samples show similar values of the magnetic entropy and adiabatic temperature changes. The large magnetocaloric effect is due to suppression of the spin entropy associated with the localized 4f moment of Eu 2+ ions. The giant magnetocaloric effect, together with negligible hysteresis, suggest that EuTiO 3 could be a potential material for magnetic refrigeration below 40 K.

We show the emergence of fractional quantum Hall states in graphene grown by chemical vapor deposition (CVD) for magnetic fields from below 3 T to 35 T where the CVD-graphene was dry-transferred. Effective composite-fermion filling factors up to ν * = 4 are visible and higher order composite-fermion states (with four flux quanta attached) start to emerge at the highest fields. Our results show that the quantum mobility of CVD-grown graphene is comparable to that of exfoliated graphene and, more specifically, that the p/3 fractional quantum Hall states have energy gaps of up to 30 K, well comparable to those observed in other silicon-gated devices based on exfoliated graphene.

Despite several attempts, the intimate electronic structure of two-dimensional electron systems buried at the interface between LaAlO 3 and SrTiO 3 still remains to be experimentally revealed. Here, we investigate the transport properties of a high-mobility quasi-two-dimensional electron gas at this interface under high magnetic field (55 T) and provide new insights for electronic band structure by analyzing the Shubnikov-de Haas oscillations. Interestingly, the quantum oscillations are not 1∕B-periodic and produce a highly non-linear Landau plot (Landau level index versus 1/B). We explore different scenarios leading to 1/B-aperiodic oscillations where the charge and the chemical potential vary as the magnetic field increases. Overall, the magneto-transport data are discussed in light of high-resolution scanning transmission electron microscopy (HRSTEM) analysis of the interface as well as calculations from density functional theory.