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Coexisting static magnetic order and superconductivity in CeCu 2 Si 2 </mml:…

1991; American Physical Society; Volume: 43; Issue: 1 Linguagem: Inglês

10.1103/physrevb.43.83

1095-3795

Cheng Tien,

Physics of Superconductivity and Magnetism

$^{63}\mathrm{Cu}$ nuclear quadrupole resonance (NQR) has been observed in a heavy-fermion system ${\mathrm{CeCu}}_{2}$${\mathrm{Si}}_{2}$. In the superconducting ${\mathrm{CeCu}}_{2}$${\mathrm{Si}}_{2}$ specimens (${\mathit{T}}_{\mathit{c}}$\ensuremath{\simeq}0.6 K), NQR experiments have revealed an onset of a phase transition below \ensuremath{\sim}1 K. Zero- and longitudinal-field muon-spin-relaxation measurements suggest a static magnetic ordering below \ensuremath{\sim}0.8 K, either in the spin-glass or in incommensurate spin-density-wave states. The exotic transition observed in NQR measurements should be closely related to the static magnetic ordering in muon-spin-relaxation measurements. NQR data from a nonsuperconducting ${\mathrm{CeCu}}_{2}$${\mathrm{Si}}_{2}$ sample are consistent with extensive disorder in Cu site occupation. Therefore, the spin-density wave may be depressed in the nonsuperconducting ${\mathrm{CeCu}}_{2}$${\mathrm{Si}}_{2}$. The superconducting transition temperature ${\mathit{T}}_{\mathit{c}}$ can be enhanced by the presence of spin-density waves such that, if the spin-density wave is depressed, ${\mathrm{CeCu}}_{2}$${\mathrm{Si}}_{2}$ will lose its superconducting properties.