NQR Studies on Magnetism and Superconductivity of Oxides Superconductors

1989 Fiscal Year Final Research Report Summary

• Project/Area Number: 63540267
• Research Category: Grant-in-Aid for General Scientific Research (C)
• Allocation Type: Single-year Grants
• Research Field: 物性一般（含極低温･固体物性に対する理論）
• Research Institution: Faculty of Science, Hokkaido University
• Principal Investigator: KUMAGAI Ken-ichi Hokkaido Univ., Dept. of Physics, Associate Professor, 理学部, 助教授 (70029560)
• Co-Investigator(Kenkyū-buntansha): NAKAJIMA Haruo Hokkaido Univ., Dept. Physics, Professor, 理学部, 教授
• Project Period (FY): 1988 – 1989
• Keywords: Nuclear Magnetic Resonance / Nuclear Spin-Lattice Relaxation Time / High-T_c Superconductor / Antiferromagnetism

Research Abstract

Nuclear quadrupole resonances (NQR) of ^<139>La and ^<63,65>Cu have been investigated in the wide range of x in hole-doped La_<2-x>M_xCuO_4 (M=Sr, Ba). The divergence of the nuclear relaxation rate of ^<139>La at T_c*-10K indicates the existence of the peculiar frustrated magnetic phase between the 3D-antiferro- magnetic and superconducting phases. The spin echo signals of ^<63,65>Cu are observed between 30-50KHz in zero external field. The spectra consist of the two component of the Cu-NQR lines for x<0.4, of which origin is still unclear. Relaxation rates, 1/T_1 and 1/T_2 are much enhanced with decreasing x. The temperature dependence of 1/T_1 for x>0.4 obeys the Korringa relation, T_1T=const., below 200K.
We have confirmed the antiferromagntic order of Cu moments in the electron-doped Ln_<2-x>Ce_xCuO_4 (Ln =Nd, Pr, Sm). Unexpected observation of nuclear magnetic resonance (NMR) with vanishingly small quadrupole interactions in the Ce-doped samples suggests that the local electronic properties at Cu site in the electron-doped oxides differ from the hole-doped ones.