Diffuse x-ray scattering study of an oxygen-disordered tetragonal YBa_{2}(Cu_{0.955}Al_{0.045})_{3}O_{7} crystal

Abstract

X-ray scattering from a tetragonal single crystal of YBa2(Cuo.955Alo.o45)3C>7 shows diffuse streaking in [110] directions about the Bragg peaks. Through a quantitative calculation using a coupled concentration wave, static displacement wave approach, we show that this is essentially attributable to the shear displacement field produced by a disordered oxygen array on the Cu(0-O "chain" plane. We also observe pronounced short-range chain order (local orthorhombic fluctuations) whose correlation range is considerably greater than the superconducting coherence length. This suggests that on a scale relevant for superconductivity the (local) orthorhombicity remains important in this tetragonal structure.

Interpretation of tweed contrast from the YBa2Cu3O7-δ system

“…Skjerpe et al 1992) showed, by kinematical calculations of the diffraction intensities, that YBa,Cu,O, with an average domain size below about 20 nm will appear tetragonal when only the fundamental reflections are considered. On the other hand, through calculations using a coupled concentration wave-static displacement wave approach, Jiang et al (1991) and Cai, Zhu and Welch (1992) generated excellent matches of intensity profile of the diffuse scattering in the a*-b* plane to that observed in X-ray and TEM experiments. They concluded that the shear displacement field (Huang scattering) produced by randomly distributed oxygen (Jiang et al 1991) or oxygen clustering (Cai et al 1992) on the C u ( l k 0 'chain' plane is responsible for diffuse streaking in [llO] and [TlO] directions through the Bragg peaks.…”

“…On the other hand, through calculations using a coupled concentration wave-static displacement wave approach, Jiang et al (1991) and Cai, Zhu and Welch (1992) generated excellent matches of intensity profile of the diffuse scattering in the a*-b* plane to that observed in X-ray and TEM experiments. They concluded that the shear displacement field (Huang scattering) produced by randomly distributed oxygen (Jiang et al 1991) or oxygen clustering (Cai et al 1992) on the C u ( l k 0 'chain' plane is responsible for diffuse streaking in [llO] and [TlO] directions through the Bragg peaks. They also suggested that there were local orthorhombic fluctuations or orthorhombic domains in Fe-, Co-or Al-alloyed YBa,Cu,O, -& Twinning involves a shear displacement.…”

“…Wayman 1983, Shapiro et al 1986, Jiang, Wochner, Moss and Zschack 1991, Semenovskaya and Khachaturyan 1991. In the superconducting oxide YBa, (Cu, -xM,),O, tweed contrast is observed for M = Fe, Co or Al, x > 0025, and M = Cu, 6 ~0 6 4 .…”

“…system has been explained successfully (Jiang et al 1991, Cai et al 1992). However, image simulation of the tweed from the same material has not been explored.…”

Tweed in martensites: a potential new spin glass

“…8,4,20 This will produce a free energy difference (F − − F + )(x, y) which will depend on gradients of η. 2 The local elastic free energy can in general have three minima: two at ±φ 0 for the two martensitic variants, and one at φ = 0 for the austenite.…”