Spin-glass behavior in Ni-doped La1:85Sr0:15CuO4

Abstract

The dynamic and static magnetic properties of La1.85Sr0.15Cu1−yNiyO4 with Ni concentration up to y=0.63 are reported. All the features that characterize the spin-glass (SG) behavior are found: bifurcation of the dc susceptibility χ vs temperature curve, a peak in the zero-field cooling branch of this curve accompanied by a step in the imaginary part of the ac susceptibility χac, frequency dependence of the peak position in the real part of χac and scaling behavior. The decay of remnant magnetization is described by a stretched-exponential function. The characteristic time from the critical slowing-down formula that governs the dynamics of the system suggests the existence of the spin clusters. The strongest interactions between the fluctuating entities are at y equal to the charge carriers concentration in the system. The SG transition temperature decreases linearly with decreasing y for y≤0.30 and extrapolates to 0 K at y=0 what means that Ni display a magnetic character in the surrounding Cu-O network starting from the smallest concentration y. The static critical exponents characterizing the scaling behavior of the nonlinear part of χ lie between those typical for three dimensional Ising-like and Heisenberg-like systems.