Temperature dependent electronic correlation effects in GdN

Abstract

We investigate temperature dependent electronic correlation effects in the conduction bands of Gadolinium Nitride (GdN) based on the combination of many body analysis of the multi-band Kondo lattice model and the first principles TB-LMTO bandstructure calculations. The physical properties like the quasi-particle density of states (Q-DOS), spectral density (SD) and quasi-particle bandstructure (Q-BS) are calculated and discussed. The results can be compared with spin and angle resolved inverse photoemission spectroscopy (ARIPS) of the conduction bands of GdN. A redshift of 0.34 eV of the lower band edge (T=T c → T=0) is obtained and found in close comparison with earlier theoretical prediction and experimental value reported in the literature.PACS numbers: 71.10. 71.15.Mb, 71.27.+a p , where X p = N,P,As,Sb,Bi and Eu 2+ X 2− c , where X c = O,S,Se,Te can be compared since they are isoelectronic in nature. If pure ionic bonding is considered then they are expected to be insulators or semiconductors. The divalent rare earth monochalcogenides are indeed insulators or semiconductors[1, 2] but the trivalent rare earth monopnictides, especially the rare earth nitride GdN, show an intricate conducting character. For instance, the bandstructure calculations suggest GdN to be a semiconductor [3,4,5], half-metal [6,7,8] or a semiconductor in the paramagnetic and a semimetal in the ferromagnetic case using quasi-particle self energy corrections[9]. The above mentioned results used different computational techniques. Hasegawa et.al, [3] were the first to calculate the self-consistent electronic bandstructures of GdN for the paramagnetic case using augmented plane wave (APW) method. Their calculations employed one-electron potential instead of local spin density (LSD) functional theory. While Lambrecht[4] addressed the problem by estimating the gap corrections beyond local density approximation (LDA), Ghosh[5] performed self consistent spin polarized calculations using full potential linear muffin-tin orbital (FP LMTO) but with rigid shifts in the 5d and 4f states in order to fit the experimental X-ray photoemission spectroscopy (XPS) and X-ray Bremsstrahlung Isochromat spectroscopy (BIS) results. The Self Interaction Corrected local spin density (SIC-LSD) calculations by Aerts et.al, [6] and augmented spherical wave (ASW) within LDA and generalized gradient approximations (GGA) by Eyert[8] rendered half-metallic nature to GdN. There has also been an interesting investigation on the electronic structure and magnetic properties of GdN by Duan et.al,[7] based on first principles calculations as a function of unit cell volume. They found that GdN transforms first from half-metallic to semi-metallic and then finally to a semiconductor upon applying stress. These features reveal a strong lattice constant dependence on the electronic structure of GdN. However, experimental results demonstrated bulk GdN to be a low carrier semimetallic [10] or GdN thin films to be insulating [11].The magnetic properties of GdN also form a very inter...

Additional carrier-mediated ferromagnetism in GdN

“…8,9 In the latter case, the carrier concentration ͑doping͒ is usually assigned to defects such as nitrogen vacancies 9 or structural defects ͑grain boundaries between the nanocrystallites͒. 23 With realistic values of input parameters 35 such as strength of d-f exchange coupling and the single particle energies of 5d conduction band obtained using tight-binding linear muffin-tin orbital atomic-sphere approximation ͑TB-LMTO-ASA͒ 36 we evaluate the following effective exchange integrals, In above equations, Ĝ ͑0͒ ͑E͒ and Ĝ ͑E͒ are the single particle non-interacting ͑undressed͒ and interacting ͑dressed͒ Green function matrices respectively and f − ͑E͒ is the Fermi function. 34 The subscript "s" denotes the s th neighboring shell of radius R s spanning ⌬s number of neighbors to the central atom as shown in the inset of Fig.…”

“…34 We take the realistic bandstructure of 5d conduction bands as an input for the single particle energies and the d-f exchange coupling 35 to calculate the dependence of T c on carrier concentration. The results are in close proximity to the experimental findings.…”

Electronic structure of EuN: Growth, spectroscopy, and theory

“…1 Theoretical treatments predict that the series includes both half metals and ferromagnetic semiconductors. [2][3][4][5][6][7] However, treating the atomic-like 4f electrons within band theory is challenging, and the predicted electronic structures can be contradictory. Experimental investigations of the RE-Ns are also challenging, owing to the difficulty in preparing samples that are stoichiometric, and passivating them against oxidation in atmosphere.…”

Electronic, Magnetic and Transport Properties of Rare‐Earth Monopnictides

“…Later, using the same approach, Sharma and Nolting studied temperature-dependent electronic correlation effects in GdN in 2006 [113]. Assuming GdN to be a semiconductor, they obtained its quasiparticle spectral densities and density of states and found that the correlation effects were strongly temperature dependent.…”