Magnetic, Optical, and Electronic Properties of the Phosphide Oxides REZnPO (RE = Y, La–Nd, Sm, Gd, Dy, Ho)

Abstract

Well‐shaped yellow to red transparent single crystals of the phosphide oxides REZnPO (RE = Y, La–Nd, Sm, Gd, Dy, Ho) were synthesized from the elements and ZnO in NaCl/KCl fluxes in sealed silica ampoules. Four structures (NdZnPO type, R3m) were refined from single crystal X‐ray diffractometer data: a = 388.5(2), c = 3032(1) pm, wR2 = 0.0380, 360 F2 values for YZnPO, a = 394.6(2), c = 3071(1) pm, wR2 = 0.0587, 226 F2 values for SmZnPO, a = 392.2(2), c = 3056(1) pm, wR2 = 0.0262, 462 F2 values for GdZnPO, and a = 389.33(6), c = 3030.5(4) pm, wR2 = 0.0453, 217 F2 values for DyZnPO each with 14 variables per refinement. The structures are composed of alternate stacks of (RE3+O2−) and (Zn2+P3−) layers with covalent RE–O and ZñP bonding within and weak ionic bonding between the layers. The zinc and oxygen atoms have slightly distorted tetrahedral coordination by atoms of phosphorus and the rare earth element, respectively. According to the electron precise formulation RE3+Zn2+P3−O2−, these pnictide oxides are transparent in visible light. Susceptibility measurements on β‐CeZnPO, β‐PrZnPO, and GdZnPO reveal Curie‐Weiss paramagnetism with experimental magnetic moments of 2.31, 3.60, and 7.72 μB/RE atoms, respectively. β‐CeZnPO and β‐PrZnPO show antiferromagnetic order with Néel temperatures of 7.4 (Ce) and 2.2 (Pr) K. GdZnPO shows no magnetic ordering down to 2 K. Single crystal absorption spectra measured for REZnPO (RE = Y, La, Pr, Nd, Sm, Dy) in the NIR‐Vis region reveal unexpected variations for the optical band gap of these phosphide oxides. For RE = Pr, Nd, Sm, Dy, Ho f‐f electronic transitions with nicely resolved ligand‐field splittings are observed in the range 6000–20000 cm−1. DFT band structure calculations show similarity between the valence bands of tetragonal and rhombohedral REZnPO as they possess mainly P‐3p character. In both cases, the conduction bands have mainly Zn‐4s character, but a significant contribution of RE‐5d occurs in rhombohedral REZnPO, which is responsible for a smaller optical band gap for the latter compounds. Variations of the energy gaps of tetragonal REZnPO can be explained by hybridization of Zn‐4s + RE‐5d + RE‐4f orbitals for the conduction band. DFT volume optimizations of α‐ and β‐PrZnPO show β‐PrZnPO to be more stable by 10.7 kJ mol−1.

Multiple magnetic transitions in SmCoAsO

“…5 LaMnPO is proved to be an AFM semiconductor. 6 CeZnPO shows AFM order with Néel temperature of 7.4 K. 7 LaCoAsO and LaCoPO are itinerant ferromagnets with Curie temperatures of 43 and 66 K, respectively. 8 In addiction, the 3d transition metal compounds have attracted much attention to study the electron correlation effect.…”

Effects of rare-earth substitution on the stability and electronic structure of REZnOSb (RE=La–Nd, Sm–Gd) investigated via first-principles calculations

“…The bonding bands from À12 to À6 eV are mainly attributed to Sb 5s states, Zn 3p states and Zn 3d states, which result from the covalent linkage between Zn and Sb. Furthermore, weak polar interactions between O-Sb, and RE-Zn can be observed due to the overlap of O 2p states -Sb 5p states, and RE 5d states -Zn 3p states around the valence band maximum (VBM), which is similar to PrZnOP [33]. It is interesting that DOS of RE 4f states shift to the low-energy region with varying the rare-earth elements from Ce to Gd around conduction band minimum (CBM), increasing the overlap of conduction and valence bands.…”

Pnictidoxide – eine neue Klasse von Hoch‐TC‐Supraleitern

“…Erste orientierende Untersuchungen an Verbindungen mit paramagnetischen Seltenerdmetallen zeigen aber auch interessante magnetische Eigenschaften: So ist CeRuPO ein seltenes Beispiel für ein ferromagnetisches Kondo-Gitter. CeOsPO ordnet antiferromagnetisch, [23] ebenso b-CeZnPO und b-PrZnPO, [24] wohingegen die Anti-monide CeZnSbO und PrZnSbO bis zu tiefen Temperaturen paramagnetisch bleiben. [25] Erste 121 Sb-Mößbauer-spektroskopische Untersuchungen an PrMnPO und NdMnPO zeigen übertragene Hyperfeinfelder bei tiefen Temperaturen.…”

“…[24,26] Dementsprechend sind die Verbindungen SEZnPnO Halbleiter. [25] Absorptionsspektren an Einkristallen der Verbindungen SEZnPO (SE = Y, La, Pr, Nd, Sm, Dy) im NIR/VisBereich zeigen eine interessante Variation der optischen Bandlücken und f-f-Übergänge mit gut aufgelösten Ligandenfeldaufspaltungen.…”

“…[25] Absorptionsspektren an Einkristallen der Verbindungen SEZnPO (SE = Y, La, Pr, Nd, Sm, Dy) im NIR/VisBereich zeigen eine interessante Variation der optischen Bandlücken und f-f-Übergänge mit gut aufgelösten Ligandenfeldaufspaltungen. [24] Die neuen Pnictidoxid-Supraleiter werden zweifellos enormes Interesse auf sich ziehen. Ihre hohen Übergangs-temperaturen und kritischen Magnetfelder machen sie bereits jetzt für Anwendungen interessant, die derzeit von A15-Supraleitern dominiert sind.…”