Niobium nitride (NbN) has attracted scientific interest due to its diverse physical properties and a variety of structural phases. The structure and superconductivity of the cubic [Formula: see text]-NbN phase are well established, but its hexagonal phases are not explored hitherto. In the present work, we report a simple synthesis route and a detailed study of hexagonal [Formula: see text]-Nb2N thin films. Thermal annealing of sputtered grown [Formula: see text]-NbN leads to a single phase [Formula: see text]-Nb2N at 973 K as confirmed by x-ray diffraction and absorption spectroscopy. The electrical transport measurements revealed a dominance of electron–phonon interactions with a superconducting transition around 4.74 K and an upper critical field [[Formula: see text]] of 3.99 T. The estimated [Formula: see text] is well below the calculated Pauli limit, and the Maki parameter value ([Formula: see text] [Formula: see text] 1) indicates that [Formula: see text] is dominated by an orbital pair breaking effect. Finally, the obtained value of electron–phonon coupling constant ([Formula: see text]) is in excellent agreement with a weak coupling Bardeen–Cooper–Schrieffer value of conventional superconducting materials.
Chromium nitride (CrN) spurred enormous interest due to its coupled magnetostructural and unique metal-insulator transition. The underneath electronic structure of CrN remains elusive. Herein, the electronic structure of epitaxial CrN thin film has been explored by employing resonant photoemission spectroscopy (RPES) and x-ray absorption near edge spectroscopy study in combination with the first-principle calculations. The RPES study indicates the presence of a charge-transfer screened 3dn L (L: hole in the N-2p) and 3dn−1 final-states in the valence band regime. The combined experimental electronic band structure along with the orbital resolved electronic density of states from the first-principle calculations reveals the presence of Cr(3d)-N(2p) hybridized (3dn L) states between lower Hubbard (3dn−1) and upper Hubbard (3dn+1) bands with onsite Coulomb repulsion energy (U) and charge-transfer energy (Δ) estimated as ≈ 4.5 and 3.6 eV, respectively. It verifies the participation of ligand (N-2p) states in low energy charge fluctuations and provides concrete evidence for the charge-transfer (Δ<U) insulating nature of CrN thin film.
FeRh 0.8 Pd 0.2 is known to exhibit near room-temperature first-order antiferromagnetic (AF)–ferromagnetic (FM) transition, typical of chemically ordered FeRh system. In addition, it is also reported to show martensitic transition at a lower temperature. In this work, the effect of sample history on transition temperature (Tt) and the magnetocaloric effect (MCE) have been studied. The experimentally determined MCE parameters across FM to AF transition induced either by isothermal magnetic field sweep or by temperature sweep showed a large isothermal change in entropy around room temperature, i.e., 14 J/kg K for 50 kOe magnetic field change, whereas MCE corresponding to AF–FM transition depends on cooling history. Our study shows that in the presence of martensite phase, the peak value of MCE is shifted to higher temperatures but with significantly reduced magnitude.
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