High resolution X-ray scattering studies of structural phase transitions in underdoped La${}_{2-x}$Ba${}_x$CuO${}_4$

Abstract

We have studied structural phase transitions in high quality underdoped La${}_{2-x}$Ba${}_x$CuO${}_4$ single crystals using high resolution x-ray scattering techniques. Critical properties associated with the continuous High Temperature Tetragonal (HTT, $I4/mmm$) to Middle Temperature Orthorhombic (MTO, $Cmca$) phase transition were investigated in single crystal samples with x=0.125, 0.095, and 0.08 and we find that all behavior is consistent with three dimensional XY criticality, as expected from theory. Power law behavior in the orthorhombic strain, 2(a-b)/(a+b), is observed over a remarkably wide temperature range, spanning most of the MTO regime in the phase diagram. Low temperature measurements investigating the Low Temperature Tetragonal (LTT, $P{4}_2/ncm$) phase, below the strongly discontinuous MTO$\to$LTT phase transition, in x=0.125 and x=0.095 samples show that the LTT phase is characterized by relatively broad Bragg scattering, compared with that observed at related wavevectors in the HTT phase. This shows that the LTT phase is either an admixture of tetragonal and orthorhombic phases, or that it is orthorhombic with very small orthorhombic strain, consistent with the ``less orthorhombic" low temperature structure previously reported in mixed La${}_{2-x}$Sr${}_{x-y}$Ba${}_y$CuO${}_4$ single crystals. We compare the complex temperature-composition phase diagram for the location of structural and superconducting phase transitions in underdoped La${}_{2-x}$Ba${}_x$CuO${}_4$ and find good agreement with results obtained on polycrystalline samples.

8 pages, 7 figures, 1 table

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Cited by in corpus (11)

• Stripe order in superconducting La(2-x)Ba(x)CuO(4) for 0.095 <= x <= 0.155
• Progress in Neutron Scattering Studies of Spin Excitations in High-Tc Cuprates
• Evidence for unusual superconducting correlations coexisting with stripe order in La(1.875)Ba(0.125)CuO(4)
• Determination of the optical properties of La{2-x}Ba{x}CuO{4} for several dopings, including the anomalous x=1/8 phase
• Incommensurate Spin Ordering and Fluctuations in underdoped La_{2-x}Ba_{x}CuO_{4}
• Reconciliation of local and long range tilt correlations in underdoped La2-xBaxCuO4
• Diagonal and Collinear Incommensurate Spin Structures in underdoped La${}_{2-x}$Ba${}_x$CuO${}_4$
• Two Dimensional Incommensurate and Three Dimensional Commensurate Magnetic Order and Fluctuations in $L{a}_{2-x}B{a}_{x}Cu{O}_4$
• Neutron Scattering Studies of Spin-Phonon Hybridization and Superconducting Spin-Gaps in High Temperature Superconductor $L{a}_{2-x}(Sr,Ba{)}_{x}Cu{O}_4$
• Topological Doping and Superconductivity in Cuprates: An Experimental Perspective
• Critical X-ray Scattering Studies of Jahn-Teller Phase Transitions in TbV${}_{1-x}$As${}_x$O${}_4$