Rare-earth mononitrides

Abstract

When the rare earth mononitrides (RENs) first burst onto the scientific scene in the middle of last century, there were feverish dreams that their strong magnetic moment would afford a wide range of applications. For decades research was frustrated by poor stoichiometry and the ready reaction of the materials in ambient conditions, and only recently have these impediments finally been overcome by advances in thin film fabrication with ultra-high vacuum based growth technology. Currently, the field of research into the RENs is growing rapidly, motivated by the materials demands of proposed electronic and spintronic devices. Both semiconducting and ferromagnetic properties have been established in some of the RENs which thus attract interest for the potential to exploit the spin of charge carriers in semiconductor technologies for both fundamental and applied science. In this review, we take stock of where progress has occurred within the last decade in both theoretical and experimental fields, and which has led to the point where a proof-of-concept spintronic device based on RENs has already been demonstrated. The article is organized into three major parts. First, we describe the epitaxial growth of REN thin films and their structural properties, with an emphasis on their prospective spintronic applications. Then, we conduct a critical review of the different advanced theoretical calculations utilised to determine both the electronic structure and the origins of the magnetism in these compounds. The rest of the review is devoted to the recent experimental results on optical, electrical and magnetic properties and their relation to current theoretical descriptions. These results are discussed particularly with regard to the controversy about the exact nature of the magnetic state and conduction processes in the RENs.Comment: 34 pages, 14 figure

Magnetism and electronic structure calculation of SmN

“…The structural, magnetic and electronic properties of rare-earth monopnictides were reviewed recently [1,2]. In these reviews it was emphasized that the experimental data on the rare-earth monopnictides are rather scattered, and often lead to contradicting results, due to difficulties in obtaining samples of good quality.…”

“…Thus, controversies concerning their electronic structure, transport and magnetic properties exist in literature. In the same reviews [1,2] the results of different electronic structure calculations of RN compounds were also compared. The description of the strongly correlated 4f states within the band theory is shown to require methods which go beyond density functional theory (DFT) in the standard local spin density approximation (LSDA).…”

Preparation and Some Properties of Nanostructural Rare Earth Nitrides by Using the Reaction of Hydrides with Ammonia

“…One was reactive ball milling (Fritsch Ltd.: P-6) under an ammonia atmosphere and the other was high-pressure reactions (12)(13)(14) in an autoclave at 473-573 K for 48 h. In a typical preparation of cerium amide by ball milling [19], cerium dihydride (0.25 g) was placed in a grinding bowl (made of zirconia; volume of 45 cm 3 ), followed by introduction of 0.3 MPa ammonia. The mixtures were subjected to ball milling with zirconia balls (diameter: 3 mm, 55 g) for 0.25-20 h, operated at 650 rpm.…”

“…There have been studies reported on many processes for the preparation of nitrides [14,15], but none is fully satisfactory for catalysts. The direct reaction of RE metals with ammonia or nitrogen at elevated temperatures is undesirable for the preparation of stoichiometric nitrides [16].…”

Fully opposite spin polarization of electron and hole bands in DyN and related band structures of GdN and HoN

“…2 For a recent discussion and extensive overview of the literature, see Ref. 1. On the experimental side, this uncertainty is related to the difficulty in achieving purely stoichiometric 1:1 RE:N ratio.…”