Magnetic stress as a driving force of structural distortions: the case of CrN

We show that the observed transition from rocksalt to orthorhombic P$_{nma}$ symmetry in CrN can be understood in terms of stress anisotropy. Using local spin density functional theory, we find that the imbalance between stress stored in spin-paired and spin-unpaired Cr nearest neighbors causes the rocksalt structure to be unstable against distortions and justifies the observed antiferromagnetic ordering. This stress has a purely magnetic origin, and may be important in any system where the coupling between spin ordering and structure is strong.Comment: 4 pages (two columns) 4 figure

Competition between Magnetic and Structural Transition in CrN

CrN is observed to undergo a paramagnetic to antiferromagnetic transition accompanied by a shear distortion from cubic NaCl-type to orthorhombic structure. Our first-principle plane wave and ultrasoft pseudopotential calculations confirm that the distorted antiferromagnetic phase with spin configuration arranged in double ferromagnetic sheets along [110] is the most stable. Antiferromagnetic ordering leads to a large depletion of states around Fermi level, but it does not open a gap. Simultaneous occurence of structural distortion and antiferromagnetic order is analyzed.Comment: 10 pages, 10 figure

Synthesis and structure of a new oxynitride Ba3W2O6N2

A new oxynitride Ba3W2O6N2 has been synthesised from the ammonolysis of Ba3W2O9. This compound crystallises in a hexagonal structure with a = 5.993(2) and c=21.40(4) Angstrom. Transmission electron microscopy (TEM) studies were carried out to elucidate the structure of this new compound. IR and Raman data are consistent with the C-3v site symmetry of the (WO3N)(3-) unit. This compound is isostructural with Ba3V2O8 reported in the literature

Synthesis of new transition metal nitrides, MWN2 (Mtriple bond; length as m-dashMn, Co, Ni)

We report the synthesis of ternary transition metal nitrides of the formula MWN(2) for M=Mn, Co, Ni by reaction of the corresponding MWO(4) with NH3 gas at 600-700 degrees C. MnWN2 is isostructural with the already-known FeWN2, crystallizing in a hexagonal structure (a=2.901(2), b=16.48(5) Angstrom) related to LiMoN2. CoWN2 and NiWN2 (which are isostructural amongst themselves) adopt a different hexagonal structure with a smaller c parameter. While the Mn and Fe nitrides are semiconducting, the Co and Ni nitrides are semimetallic

Anisotropic electrical transport property in La4BaCu5O13+δLa_{4}BaCu_{5}O_{13+{\delta}} and La4BaCu4NiO13+δLa_{4}BaCu_{4}NiO_{13+{\delta}} epitaxial thin films

Epitaxial films of La4BaCu5O13+delta and La4BaCu4NiO13+delta oxides are grown with a-b plane parallel to (100) of LaAlO3 and SrTiO3 by pulsed-laser deposition. The conductivity measurements performed along the c direction using LaNiO3 as the electrode show metallic behavior whereas they show semiconducting behavior in the a-b plane. Anisotropic transport property of these thin films is explained on the basis of nearly 180 degrees connected Cu-O-Cu chains with an average Cu-O distance of 1.94 Angstrom along the c direction and nearly 180 degrees and 90 degrees connected Cu-O-Cu chains in the a-b plane with short and long Cu-O distances ranging from 1.863 to 2.303 Angstrom. YBa2Cu3O7-x has been grown along (00l) on La4BaCu5O13+delta and shows a T-c of 88 K. (C) 1999 American Institute of Physics. [S0003-6951(99)04937-2]

Anisotropic electrical transport property in La4BaCu5O13+δ and La4BaCu4NiO13+δ epitaxial thin films

Epitaxial films of La4BaCu5O13+δ and La4BaCu4NiO13+δ oxides are grown with a-b plane parallel to (100) of LaAlO3 and SrTiO3 by pulsed-laser deposition. The conductivity measurements performed along the c direction using LaNiO3 as the electrode show metallic behavior whereas they show semiconducting behavior in the a-b plane. Anisotropic transport property of these thin films is explained on the basis of nearly 180° connected Cu–O–Cu chains with an average Cu–O distance of 1.94 Å along the c direction and nearly 180° and 90° connected Cu–O–Cu chains in the a-b plane with short and long Cu–O distances ranging from 1.863 to 2.303 Å. YBa2Cu3O7−x has been grown along (00l) on La4BaCu5O13+δ and shows a Tc of 88 K

Synthesis, structure, and properties of LiWN<SUB>2</SUB>

We report the synthesis of a new ternary nitride LiWN2 by the reaction of Li2WO4 with NH3 at 745&#176;C. The compound crystallizes in a layered hexagonal structure with a = 2.863 and c = 15.608 &#197;. LiWN2 is metallic, consistent with its structure with W(V) in trigonal prismatic coordination and Li1+ in octahedral coordination