Browsing by Author "Huang, MJ"

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    Determination of hole distribution in Sr14-xCaxCu24O41 using soft x-ray absorption spectroscopy at the Cu L3 edge.
    (American Physical Society, 2013-07-22) Huang, MJ; Deng, G; Chin, YY; Hu, ZW; Cheng, JG; Chou, FC; Conder, K; Zhou, JS; Pi, TW; Goodenough, JB; Lin, HJ; Chen, CT
    The physical properties of Sr14-xCaxCu24O41 are determined by the hole distribution between the edge-shared CuO2 chain and the corner-shared Cu2O3 two-leg ladder, but inconsistent results on the hole distribution were obtained in various experimental works in recent decades. In this work we reinvestigate the hole distribution by soft x-ray absorption spectroscopy at the Cu L-3 edge. By comparing with the pure ladder and the pure chain systems, we can unambiguously distinguish between the hole distributions in the chain and the ladder. We have found that there are 5.3 holes in the edge-shared chain and 0.7 holes in the corner-shared ladder on average for Sr14Cu24O41. Upon Ca substitution, the holes gradually transfer from the edge-shared chain to the corner-shared ladder, and there are up to 1.21 holes in the corner-shared ladder for Sr1.8Ca12.2Cu24O41. © 2013, American Physical Society.
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    Direct evidence of Ni magnetic moment in TbNi2Mn—X-ray magnetic circular dichroism
    (Elsevier, 2014-12-01) Yu, DH; Huang, MJ; Su, HC; Lin, HJ; Chen, CT; Campbell, SJ; Wang, JL
    We have investigated the individual magnetic moments of Ni, Mn and Tb atoms in the intermetallic compound TbNi2Mn in the Laves phase (magnetic phase transition temperature TC ~131 K) by X-ray magnetic circular dichroism (XMCD) studies at 300 K, 80 K and 20 K. Analyses of the experimental results reveal that Ni atoms at 20 K in an applied magnetic field of 1 T carry an intrinsic magnetic moment of spin and orbital magnetic moment contributions 0.53±0.01 μB and 0.05±0.01 μB, respectively. These moment values are similar to those of the maximum saturated moment of Ni element. A very small magnetic moment of order <0.1 μB has been measured for Mn. This suggests that Mn is antiferromagnetically ordered across the two nearly equally occupied sites of 16d and 8a. A magnetic moment of up to ~0.3 μB has been observed for the Tb atoms. Identification of a magnetic moment on the Ni atoms has provided further evidence for the mechanism of enhancement of the magnetic phase transition temperature in TbNi2Mn compared with TbNi2 (TC~37.5 K) and TbMn2 (TC~54 K) due to rare earth–transition metal (R–T) and transition metal–transition metal (T–T) interactions. The behaviour of the X-ray magnetic circular dichroism spectra of TbNi2Mn at 300 K, 80 K and 20 K – above and below the magnetic ordering temperature TC ~131 K – is discussed. © 2014 Elsevier