The electronic structure, formation energy, and transition energy levels of intrinsic defects have been studied using the density-functional method within the generalized gradient approximation for neutral and charged oxygen vacancy in CaCu₃Ti₄O₁₂ (CCTO). It is found that oxygen vacancies with different charge states can be formed in CCTO under both oxygen-rich and poor conditions for nonequilibrium and higher-energy sintering processes; especially, a lower formation energy is obtained for poor oxygen environment. The charge transition level (0/1+) of the oxygen vacancy in CCTO is located at 0.53 eV below the conduction-band edge. The (1+/2+) transition occurs at 1.06 eV below the conduction-band edge. Oxygen vacancies of Vo¹⁺ and Vo²⁺ are positive stable charge states in most gap regions and can act as a moderately deep donor for Vo¹⁺ and a borderline deep for Vo²⁺, respectively. The polarization and dielectric constant are considerably enhanced by oxygen vacancy dipoles, due to the off-center Ti and Cu ions in CCTO.

A novel family of two-dimensional (2D) crystalline metal superhalogens V ₃ X ₈ (X = F, Cl, Br, I) with intrinsic magnetism was predicted using first-principles calculations in the framework of density functional theory (DFT).

Resistance measurement, in situ optical microscopic observation, thermal and magnetic measurements have been carried out on Ni₅₀Mn₃₄In_15.5Al_0.5 alloy. The existence of a pronounced premartensitic transition prior to martensitic transition can be characterized by microstructure evolution as well as exothermic peak and smooth decrease of resistance and magnetization with obvious hysteresis over a wide temperature range upon cooling. Consequently, the alloy undergoes two successive magneto-structural transitions consisting of premartensitic and martensitic transitions. Magnetoelastic coupling between magnetic and structural degrees of freedom would be responsible for the appearance of premartensitic transition, as evinced by the distinct shift of transitions temperatures to lower temperature with external applied field of 50 kOe. The inverse premartensitic transition induced by magnetic field results in large magnetoresistance, and contributes to the enhanced inverse magnetocaloric effect through enlarging the peak value and temperature interval of magnetic entropy change ΔS_m.

Effect of thermal cycle on the interfacial antiferromagnetic (AFM) spin configuration and exchange bias in Ni₅₀Mn₃₆Sb₁₄ alloy has been investigated. The results indicate thermal cycle can induce further martensitic transition from part of arrested FM phase to AFM phase, leading to the reconstruction of interfacial antiferromagnetic spin configuration. The shape of hysteresis loops at 5 K after cooling back can be tuned from a single-shifted loop to a nearly symmetric double-shifted loop gradually accompanied with exchange bias field increasing to peak value and then decreasing. The evolutions can be illustrated intuitively by a simple AFM bidomain model.