Influence of substrate strain on La580'3Pr0'3Ca38MnO3 phase transition

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Influence of substrate strain on
La5/8-0.3Pr0.3Ca3/8MnO3 phase transition

• Dane Gillaspie1,2, J. X. Ma1,2, Hong-Ying Zhai1,
  T. Z. Ward1,2, H. M. Christen1, E. W.
  Plummer1,2, J. Shen1,2
• 1Material Science and Technology Division, Oak
  Ridge National Laboratory, Oak Ridge, Tennessee,
  37831
• 2Department of Physics and Astronomy, University
  of Tennessee, Knoxville, Tennessee 37996

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LPCMO La1-x-yPryCaxMnO3
M. Uehara et al, Nature 399, 56 (1999)
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LPCMO La1-x-yPryCaxMnO3
Change the average A-site size
From Cheong, S.-W. Hwang, H.Y. in Colossal
Magnetoresistance Oxides (1999)
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Why La5/8-0.3Pr0.3Ca3/8MnO3?
CO
FM
M. Uehara et al, Nature 399, 56 (1999)
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Important Question

• What is the underlying mechanism that controls
  phase separation?
• Quenched disorder
• Dagotto, E. (2003). Nanoscale Phase Separation
  and Colossal Magnetoresistance The Physics of
  Manganites and Related Compounds. Berlin,
  Springer Verlag.
• Self-organization
• Ahn, K. H., T. Lookman, A. R. Bishop (2004).
  Strain-induced metal-insulator phase coexistence
  in perovskite manganites. Nature 428 401 - 404.

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Characterization
Growth Laser-MBE
X-ray diffraction Film Quality Strain State
Atomic Force Microscopy Film Morphology
SQUID Magnetometry Moment vs. Temperature Moment
vs. Field
Base Pressure 1?10 -10 torr Growth Oxygen
Pressure 0.5 mtorr Growth Temperature
820C Post-growth anneal 5hrs at 850C
PPMS Resistance vs. Temerature Resistance vs.
Field
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Different substrates
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Magnetic Structure 90nm LPCMO
STO substrate large tensile strain enhances CO
phase
LAO substrate compressive strain suppresses CO
phase
SLGO substrate negligible strain
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Magnetoresistance measurements 30nm LPCMO
STO and NGO (tensile strain) enhance CO phase
SLGO and LAO (compressive strain) have broad
hysteresis at zero field
H0T
R(T)/R(300K)
H3.5T
Some hysteresis at 3.5T
Charge-ordering defeated at 3.5T
H6.5T
Metal-Insulator transition at 6.5T in STO and NGO
Temperature (Kelvin)
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90nm thick samples
Thicker samples have less strain
Long-range charge ordering much less stable in
thick sample
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Conclusions

• Tensile strain enhances long-range charge-ordered
  state.
• Compressive strain enhances short-range
  charge-ordered state.
• Small changes in strain can yield large changes
  in balance between CO and FM states.

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Xray Residual Space Maps
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What is LPCMO?
La1-xCaxMnO3
Pr1-xCaxMnO3

• La1-x-yPryCaxMnO3

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