Magnetic Nature of a Ni Dopant in La_{1.85}Sr_{0.15}CuO_{4}: Spin-Glass Behavior |

A. Malinowski, V.L. Bezusyy, R. Minikayev, W. Paszkowicz, P. Dziawa, Y. Syryanyy and M. Sawicki
Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warsaw, Poland |

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The magnetic properties of La_{1.85}Sr_{0.15}CuO_{4} doped with Ni was investigated in the field up to 5 T and in the temperature range from 2 K to 400 K using both dc and ac techniques. For Ni content larger than 0.05 the system exhibits irreversibility of low-field susceptibility χ(T) below a certain temperature depending on y and a cusp at T_{g} in χ(T) measured after zero-field cooling. The decay of remnant magnetization below T_{g} with time is described by a stretched-exponential function. In accordance with scaling theory, all the χ(T) data for y = 0.50 sample taken in the vicinity of T_{g} at different fields collapse onto two separate curves when plotted as q|t|^{-β} vs. B^{2} |t|^{-β - γ}, where q is the spin-glass order parameter, t = (T - T_{g})/T_{g}, and β and γ are the critical exponents. All these features taken together reveal existence of spin-glass phase below T_{g}. Variation of T_{g} with y is linear below y = 0.25 and T_{g} extrapolates to 0 K for y → 0 what strongly suggests that spin-glass phase extends into superconducting region of the phase diagram. |

DOI: 10.12693/APhysPolA.118.244 PACS numbers: 74.62.Dh, 75.40.Cx, 75.40.Gb, 75.50.Lk |