Synthesis and magnetic properties of novel Ln{sub 2-x}M{sub x}CuO{sub 4+y} compositions (Ln = La, Pr, Nd, Sm, Eu, Gd; M = Ca, Sr, Ba; 0 {le} x {le} 0.2; {minus}0.5 {le} y {le} 0.5)

Thesis/Dissertation · Mon Mar 01 04:00:00 EST 1993

OSTI ID:10143458

Cho, Jin Hyung

Ln{sub 2}CuO{sub 4} undergo transitions to reduced Ln{sub 2}CuO{sub 4-d} (Ln = La, d = 1/3; Ln = Pr, Nd, Sm, Eu, Gd, d = 1/2). The Nd{sub 2}CuO{sub 4-type} (T{prime}-phase) La{sub 2}CuO{sub 4+d} is observed after reoxidation of La{sub 2}CuO{sub 3.67} below 500C. The magnetic properties of T/O (K{sub 2}NiF{sub 4-type}) La{sub 2}CuO{sub 4} behaves differently compared with solid-state-reacted La{sub 2}CuO{sub 4}. Implications of these nonsuperconducting behaviors within superconducting carrier densities are discussed from structural point of view. La{sub 2-x}M{sub x}CuO{sub 4+d} (M = Ca, Sr; x = 0.05, 0.15), synthesized by low temperature route, also contain excess O. {sup 139}La NQR of nonsuperconducting La{sub l.85}Sr{sub 0.15}CuO{sub 4.04} show metallic properties. Tolerance factor, based on ionic radii, is to describes structures of K{sub 2}NiF{sub 4} related cuprates. With anisotropic thermal motions of apical O in La{sub 2}CuO{sub 4}, we discuss the role of out-of-plane O for stabilization of cuprate structures. Magnetic phase diagram and phase separation of La{sub 2-x}Sr{sub x}CuO{sub 4+ {delta}} are reported. From Tc decrease by doping we infer localization and pair-breaking induced by doped holes. Phase separation is realized with antiferromagnetism. We also observe scaling properties of susceptibilities versus renormalized temperatures and infer the finite size effects by doped holes. {sup 139}La NQR spin-lattice relaxation are presented for La{sub 2-x}Sr{sub x}CuO{sub 4}, x = 0.02 to 0.08. The rate below {approximately}2T{sub N}(x) shows a power-law critical behavior while above it rate is exponential with a small x-dependent spin-stiffness constant. The spin-lattice relaxation arises from fluctations of staggered magnetization in locally ordered mesoscopic domains. Magnetically ordered state is not a conventional spin glass.

• Research Organization: Ames Lab., IA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 10143458
• Report Number(s): IS-T--1536; ON: DE93011359
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204
360207
665100
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BARIUM OXIDES
CALCIUM OXIDES
CUPRATES
EUROPIUM OXIDES
GADOLINIUM OXIDES
HIGH-TC SUPERCONDUCTORS
LANTHANUM 139
LANTHANUM OXIDES
MAGNETIC PROPERTIES
NEODYMIUM OXIDES
NUCLEAR QUADRUPOLE RESONANCE
PHASE DIAGRAMS
PHASE STUDIES
PHYSICAL PROPERTIES
PRASEODYMIUM OXIDES
SAMARIUM OXIDES
SPIN-LATTICE RELAXATION
STOICHIOMETRY
STRONTIUM OXIDES
SYNTHESIS