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A magnetic analog of the isotope effect in cuprates

A magnetic analog of the isotope effect in cuprates. Amit Keren. Ph.D. Amit Kanigel Ph.D. Rinat Ofer MSc . Yuval Lubashevsky Ph.D. Eran Amit Ph.D. Gil Drachuck. Collaborators G. Bazalitski -Technion A. Knizhnik -Technion J. Lord-ISIS Amato-PSI O. Chmaissem -ANL Wilds-ILL

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A magnetic analog of the isotope effect in cuprates

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  1. A magnetic analog of the isotope effect in cuprates Amit Keren Ph.D. Amit Kanigel Ph.D. Rinat Ofer MSc. Yuval Lubashevsky Ph.D. Eran Amit Ph.D. Gil Drachuck • Collaborators • G. Bazalitski-Technion • A. Knizhnik-Technion • J. Lord-ISIS • Amato-PSI • O. Chmaissem-ANL • Wilds-ILL • P. Lemmens-Braunschweig • E. Razzoli & M. Shi -PSI

  2. What is superconductivity? Resistivity Magnetization

  3. Superconductivity Fermions Attraction BCS Isotope effect

  4. What are HTSC’s? ~15% Y1Ba2Cu3Oy Y Cu Ba O

  5. The Isotope Effect C. A. Reynolds et. al., Phys. Rev. 84, 691 (1950). B. Serin et al., Phys. Rev. 86, 162 (1952). E. Maxwell et al., Phys. Rev. 95, 333 (1954). • Maximum 4% variation of Tc in Sn. • The (0,0) point is important. • The is not applicable for different materials.

  6. Our motivation To make a magnetic measurement equivalent of the isotope effect. We would like to change J,with no other structural changes, and see the effect on Tc. AFM PG SC SG • We will know that we changed J if TN changes. • Experimentally this is difficult but not inconceivable.

  7. CLBLCO; Our Model Compound • YBa2Cu3Oy structure. • Tetragonal at all x and y. • 2 planes per unit cell. • Over doping is possible. • Tc variation of 30%. • Valance Ca=Ba=2, La=3. • Similar level of disorder. Goldschmidt et al., Phys. Rev. B 48, 532 1993 CLBLCO allows Tcmax variations, with minimal structural changes.

  8. The role of x(CaxLa1-x)(Ba1.75-xLa0.25+x)Cu3Oy + + • Positive change is moving out with increasing x. • This alters the oxygen position.

  9. O q Cu Cu Structural variation between families (CaxLa1-x)(Ba1.75-xLa0.25+x)Cu3Oy a • Buckling angle and distance decreases with increasing x.

  10. J variations between families. (CaxLa1-x)(Ba1.75-xLa0.25+x)Cu3Oy • Jincreases with x mainly due to decreasing buckling angle. • We will verify this by TN and Tg measurements using mSR.

  11. Principals of mSR

  12. Principals of mSR Asymmetry = (F-B)/(F+B) Pz(t). Random Field Uniform Field Asymmetry Time Time

  13. Raw Zero Field mSR Data • There are oscillations in the ordered phase but not in the spin glass phase.

  14. Phase Diagram of (CaxLa1-x)(Ba1.75-xLa0.25+x)Cu3Oy • The family with the highest Tcmax has the highest TN at zero doping.

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