An exceptional kind of spin splitting in the band structure of AlN/GdN/AlN double heterostructures has been studied by employing temperature-dependent spectroscopy. This spin splitting can be attributed to both the band-gap shrink and the difference between minority and majority band energies in GdN below the Curie point; these results have been established by evaluating the optical band gaps at the X-point. The temperature-dependent magnetization measurements that provide direct evidence of the magnetic ordering below 32 K and it is described by long-range spin correlation in GdN.

Quantitative analysis of the angle dependence of planar Hall effect observed in ferromagnetic GaMnAs film J. Appl. Phys. 105, 07C501 (2009); 10.1063/1.3055354 Co-doped TiO 2 films grown on glass: Room-temperature ferromagnetism accompanied with anomalous Hall effect and magneto-optical effect Appl. Phys. Lett. 94, 102515 (2009); 10.1063/1.3095664 Microstructure, magnetic, and optical properties of sputtered Mn-doped ZnO films with high-temperature ferromagnetism

The effect of praseodymium (Pr), an amphoteric substituent, on phase transition, dielectric relaxation and electrical conductivity has been studied and analysed in 0.5Ba(ZrTi)O-0.5(BaCa)TiO (BCZT) ceramics synthesized by a solid state reaction method. Structural investigations showed co-existence of two phases - tetragonal (P4mm) and rhombohedral (R3m) - for compositions with x ≤ 0.05 wt% Pr. Temperature dependent dielectric studies revealed two phase transitions - rhombohedral (R) → tetragonal (T) and T → cubic (C) - that gradually evolved into one T → C transition for x > 0.05 wt% Pr in BCZT. A dielectric relaxation behaviour was observed in the temperature range of 275-500 °C that was attributed to the localized relaxation process (short-range hopping motion of oxygen vacancies) in the bulk of the material. Grain and grain boundary conductivity evaluated from the impedance data revealed that Pr acts as a donor dopant for x ≤ 0.05 wt% while it is an acceptor for higher concentration, in accordance with XRD observations. Defect chemistry analysis for better interpretation of the acquired data is presented. Frequency and temperature dependent ac conductivity studies were also performed and the obtained activation energy values were associated with possible conduction mechanisms.

Using the near-infrared (NIR) absorbance spectroscopy, electronic transitions and spin polarization of the GdN epitaxial film have been investigated; and the GdN epitaxial film was grown by a reactive rf sputtering technique. The GdN film exhibited three broad bands in the NIR frequency regimes; and those bands are attributable primarily to the minority and majority spin transitions at the X-point and an indirect transition along the Γ-X symmetric direction of GdN Brillouin zone. We experimentally observe a pronounced red-shift of the indirect band gap when cooling down below the Curie temperature which is ascribed to the orbital-dependent coulomb interactions of Gd-5dxy electrons, which tend to push-up the N-2p bands. On the other hand, we have evaluated the spin polarization of 0.17 (±0.005), which indicates that the GdN epitaxial film has almost 100% spin-polarized carriers. Furthermore, the experimental result of GdN electronic transitions are consistent with the previous reports and are thus well-reproduced. The Arrott plots evidenced that the Curie temperature of GdN film is 36 K and the large spin moment is explained by the nitrogen vacancies and the intra-atomic exchange interaction.

The electronic structure of a single Na monolayer on the surface of single-crystal HfSe2 is investigated using angle-resolved photoemission spectroscopy. We find that this system exhibits an almost perfect "nearly-free-electron" behavior with an extracted effective mass of ∼ 1me, in contrast to heavier masses found previously for alkali metal monolayers on other substrates. Our densityfunctional-theory calculations indicate that this is due to the large lattice constant, causing both exchange and correlation interactions to be suppressed, and to the weak hybridization between the overlayer and the substrate. This is therefore an ideal model system for understanding the properties of two-dimensional materials.