Calorimetric study of copper ordering in the T' (214) system

Correlation between weak ferromagnetism and crystal symmetry inGd2CuO4-type cuprates

“…Residual B int observed above T N ͑Cu͒ may be due to the simplified formula used or from the intrinsic 2D short-range quantum spin fluctuation. 7 The small internal field of 720 G observed for Gd 2 CuO 4 is consistent with this small saturation moment m s . Since the structural-related canting angle (T) is temperature dependent, the saturation moment m s (T) in each WF domain wall and the internal exchange field B int (T) will also be temperature dependent.…”

“…Extensive magnetic and structural studies on Gd 2 CuO 4 ͑Refs. 1-15͒ and related compounds (Gd,M ) 2 CuO 4 ͑M ϭR 3ϩ rare earths, Ce 4ϩ , Sr 2ϩ , or Bi 3ϩ ͒, [3][4][5][7][8][9][10]14 and metastable systems R 2 CuO 4 (RϭY, Tb-Tm) and related compounds [16][17][18][19][20][21] are reported. Since the occurrence of weak ferromagnetism requires an additional antisymmetric Dzyaloshinsky-Moriya-type exchange interaction term in otherwise symmetric Cu-O-Cu superexchange interaction, it is speculated that a slight oxygen distortion in the CuO 2 layer is necessary for Cu WF/CAF order in the Gd 2 CuO 4 -type cuprates.…”

“…Since the occurrence of weak ferromagnetism requires an additional antisymmetric Dzyaloshinsky-Moriya-type exchange interaction term in otherwise symmetric Cu-O-Cu superexchange interaction, it is speculated that a slight oxygen distortion in the CuO 2 layer is necessary for Cu WF/CAF order in the Gd 2 CuO 4 -type cuprates. 2,[5][6][7][8][9][10][11][12][13][14] Although single-crystal x-ray diffraction on Gd 2 CuO 4 gives a good fitting using the tetragonal TЈ-phase space group 14/mmm with Cu͑0,0,0͒ and oxygen O͑1͒͑0, 1 2 ,0͒ in CuO 2 layer formed a perfect square-planar arrangement, 1 large plane oxygen mean-square displacement U eq of 2.5 Å 2 at room temperature indicates that stable oxygen position may not be in the ideal ͑0, 1 2 ,0͒ sites. Single-crystal neutron diffraction of 158 Gd 2 CuO 4 based on TЈ-phase structure shows that Cu moments order below T N ͑Cu͒ to a basically AF structure with the propagation vector kϭ( 1 2 , 1 2 ,0) and the Cu moments are oriented parallel to the ͓110͔ direction of the tetragonal basal plane.…”

Analysis by fast-atom bombardment tandem mass spectrometry of phosphatidylcholine isolated from heart mitochondrial fractions: Evidence of incorporation of monohydroxylated fatty acyl moieties

“…Our discovery has another important biological implication: It implies that mitochondrial membranes could serve as a source of hydroxylated C-16 ana C-18 fatty acids that, like hydroxylated derivatives of arachidonic acid, could have potent biological activities. Several biological roles indeed already have been ascribed to fatty acids that are identical [18][19][20][21][22][23] or closely related [24][25][26][27][28] to those we found in the mitochondrial fractions.…”