Magnetic Nature of a Ni Dopant in La_1.85Sr_0.15CuO₄: Spin-Glass Behavior

Abstract

The magnetic properties of La1.85Sr0.15CuO4 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.

Interplay of Competing Magnetic Interactions in Noncentrosymmetric Nd3Te4 for Enhancing the Magnetocaloric Properties

“…This suggests weaker strength of coupling and thus supports the canonical glass-like nature of interacting entities having similarity with other investigated glass systems. 47,52,54,55 Further, the Tholence criterion (T f − T 0 )/T 0 is used as the glassiness parameter 56 and calculated to be ≈0.04, consistent with the reported values for other canonical spin glass systems. 51,56,57 In addition, the field-dependent ac-χ(H) data have been measured extensively and discussed for signatures of magnetic nontriviality in the Supporting Information (Figure S5).…”

“…47−50 Furthermore, dynamic scaling theory can be applied to have an adequate comprehension of the frequency dependence of T f . 51,52 According to this theory, the critical slowing down behavior of spin dynamics is described by the relation i k j j j j j j y…”

“…The derived parameters are useful to classify spin glasses into various categories. For a conventional spin glass system, zν′ and τ 0 have values in the range of 4−12 and 10 −10 to 10 −13 s, respectively, 51,52 while for a cluster glass system, τ 0 lies between 10 −7 and 10 −10 s. 53 The smaller value of τ 0 indicates the presence of interaction among smaller magnetic entities, and it is likely to have the absence of magnetic clustering. In systems with magnetic clustering, the magnetic entities interact strongly resulting in a larger relaxation time.…”

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

“…[39], we have fitted χ(T ) to the formula χ(T ) = χ 0 + A • F (T /T max ) + C/T and have calculated the effective magnetic moment introduced by Ni ion, µ ef f , from the Curie term, C/T = N µ 2 ef f /3k B T , with the rest of parameters having their usual meaning (see Ref. [52]). The moment µ ef f is constant up to y=0.07 and equal to (0.7 ± 0.05)µ B per Ni ion, what is very close to the value found previously when a linear function instead of F has been used in the analysis.…”