Nuclear magnetic resonance: Its role as a microscopic probe of the electronic and magnetic properties of High-T_c superconductors and related materials

Thesis/Dissertation · Wed Dec 27 00:00:00 EST 1995

DOI:https://doi.org/10.2172/205642· OSTI ID:205642

Suh, Byoung Jin ^[1]

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1. Iowa State Univ., Ames, IA (United States)

NMR experiments are reported for Sr₂CuO₂Cl₂, HgBa₂CuO_4+d, YNi₂B₂C and YBa₂Cu₃O₇. NMR studies typify three different aspects of microscopic properties of HTSC. In non-superconducting antiferromagnetic (AF) prototype Sr₂CuO₂Cl₂, we used NMR to investigate Cu²⁺ correlated spin dynamics and AF phase transition in CuO₂ layers. In the superconductors, we used NMR both to investigate the electronic properties of the Fermi-liquid in normal and superconducting states and to investigate flux lattice and flux-line dynamics in the superconducting state in presence of magnetic field. A summary of each study is given: ³⁵Cl NMR was measured in Sr₂CuO₂Cl₂ single crystals with T_N=257K. ₃₅Cl NMR relaxation rates showed crossover of Cu²⁺ spin dynamics from Heisenberg to XY-like correlation at 290 K well above T_N. A field-dependent T_N for H$$\perp$$c was observed and explained by a field-induced Ising-like anisotropy in ab plane. ¹⁹⁹Hg NMR was measured in HgBa₂CuO_4+d. Properties of the Fermi-liquid are characterized by a single-spin fluid picture and opening of a spin pseudo-gap at q=0 above T_c. Below T_c spin component of Knight shift decreases rapidly in agreement with prediction for d-wave pairing scheme. ¹¹B and ⁸⁹Y NMR/magnetization were measured in YNi₂B₂C. Temperature dependence of ¹¹B Knight shift and of the NSLR gave a normal state which agrees with the Korringa relation, indicating that the AF fluctuations on the Ni sublattice are negligible. Opening of the superconducting gap obeys BCS. A NMR approach to investigate vortex thermal motion in HTSC is presented, based on contribution of thermal flux-lines motion to both T₂^-1 and T₁^-1. Effects are demonstrated in YBa₂Cu₃O₇and HgBa₂CuO_4+d.

• Research Organization: Ames Lab., Ames, IA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 205642
• Report Number(s): IS-T-1767; ON: DE96006803; TRN: 96:009377
• Resource Relation: Other Information: TH: Thesis (Ph.D.); PBD: 27 Dec 1995
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
HIGH-TC SUPERCONDUCTORS
NMR SPECTRA
FERMI GAS
MAGNETIC FIELDS
MAGNETIC FLUX