Evidence for spin-glass states and Griffiths singularities in Nd_0.75Sr_1.25CoO₄

Abstract

The magnetic properties of Nd 0.75 Sr 1.25 CoO 4 have been investigated by means of dc magnetization, ac susceptibility and electron spin resonance measurements. The specimen presented a deviation from the Curie-Weiss law at T G ∼ 230 K, ferromagnetic behaviour below T C ∼ 179 K, and a cusp structure at T SG ∼ 18 K in dc magnetization. The cusp was confirmed to be due to the existence of spin-glass states, and the deviation was argued to be a Griffiths singularity. Comparing the magnetic properties of the analogous layered cobalt oxides, the anomalous magnetic features of the specimen were attributed to the introduction of rare-earth ions, Nd 3+ .

Magnetic and Electric Properties of , () Layered Perovskites

“…Increasing of (≥ 0.70), the compounds exhibited PM behavior in a wide range of temperatures as seen in the inset of Figure 1. In addition to the PM behavior of Sr 1.3 Y 0.7 CoO 4 , spin-glass (SG) transition was observed at 10 K in agreement with other cobaltates [19,20] and manganites [13]. No traces of a Griffith phase were identified within this range of doping compared with that in similar layered perovskites [12].…”

Critical Behavior Near the Paramagnetic to Ferromagnetic Phase Transition Temperature in Sr1.5Nd0.5MnO4 Compound

“…Griffiths phases, associated with various forms of disorder, have also been reported in a number of other systems [33][34][35][36][37]. In this letter, we address the question of whether a Griffiths phase is always a precursor to the deference of values of critical exponent.…”

Magnetic Relaxation Phenomena above the Freezing Temperature in the Single Layered Cobaltite La0.75Sr1.25CoO4

“…Actually, the super‐exchange interaction of Co 3+ OCo 3+ and Co 4+ OCo 4+ and the double‐exchange interaction of Co 3+ OCo 4+ competitively coexist in La 0.75 Sr 1.25 CoO 4 . On the other hand, the inverse susceptibility curve presents a pronounced downward deviation below T G ≈ 195 K, which is a signature of Griffiths phase . The Griffiths phase was originally proposed for randomly diluted Ising ferromagnets, and in some manganites and cobaltites it is referred to the coexistence of ferromagnetic clusters within the global paramagnetic phase .…”

“…Very recently, extensive study of the single layered perovskite cobaltites Ln 2 −x Sr x CoO 4 ( Ln = La, Pr, Nd, Gd, Eu, Y) revealed rich and intriguing physical properties, such as glassy behavior, Griffiths phase, magnetoresistance, dielectric properties, and so on . Substitution of Ln 3+ by Sr 2+ induces the existence of several competing interactions, that is, the antiferromagnetic superexchange interaction Co 3+ OCo 3+ and Co 4+ OCo 4+ and the ferromagnetic double exchange interaction Co 3+ OCo 4+ .…”