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?
Magnetization
Resistivity

3. Superconductivity
Fermions
Attraction
BCS
Isotope effect

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

5. The Isotope Effect Maximum 4% variation of Tc in Sn.
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,
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. Structural variation between families
(CaxLa1-x)(Ba1.75-xLa0.25+x)Cu3Oy Cu O q a
Buckling angle and distance decreases with increasing x.

10. J variations between families.
(CaxLa1-x)(Ba1.75-xLa0.25+x)Cu3Oy
J increases 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.