Formation of Nanosize Griffiths-like Clusters in Solid Solution of Ferromagnetic Manganite and Cobaltite

Abstract

We report the existence of Griffiths phase (GP) over a wide range of x in La0.6Sr0.4Mn1−xCoxO3, the solid solution of ferromagnetic (FM) La0.6Sr0.4MnO3 and La0.6Sr0.4CoO3, from magnetization measurements. In this compound, GP arises due to the quenching of randomly distributed Co-O-Mn antiferromagnetic bonds in the FM background. In contrary to divalent doped manganites, GP in the present system can exist entirely in the metallic state above TC (for x<0.10). Based on the present study, a magnetoelectronic phase diagram is drawn.

Griffiths like robust ferromagnetism in Co 3-x Mn x TeO 6 ; ( x = 0.5, 1, 2)

“…Interestingly, the observed larger magnetic moment, which increases with Mn concentration, indicates FM cluster type interactions in our samples [24]; this is demonstrated further.…”

“…The effective magnetic moment ( ) is estimated from the CW parameter (obtained from χ -1 = (T-Θ CW )/C CW ) using relation. It can be seen that all the  -1 vs T curves follow CW law just above T GP ∼190 K (onset of downturn temperature), with an effective magnetic moment, μ eff ~ 8.97 -9.42 μ B / f. u. and PM Interestingly, the observed larger magnetic moment, which increases with Mn concentration, indicates FM cluster type interactions in our samples [24]; this is demonstrated further.…”

Facile Synthesis, Magnetic and Electric Characterization of Mixed Valence La0.75K0.25AMnTiO6 (A = Sr and Ba) Perovskites

“…As shown in the 1/χ vs T plots at 100 Oe of as-prepared samples (see the insets of Figure c,d), an abrupt downturn below the temperature T GP (∼345 K for La 0.75 K 0.25 ­SrMn­TiO 6 and ∼274 K for La 0.75 K 0.25 ­BaMn­TiO 6 ) can be interpreted properly as the existence of the Griffiths phase (GP) which is always reported in the ferromagnetic perovskites with inhomogeneous magnetic states. , In order to confirm this scenario, the magnetization measurements χ­( T ) were conducted under different applied fields. As shown in Figure c,d, the abnormal downturn in 1/χ­( T ) curves can be suppressed gradually with increasing the applied field.…”

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 .…”