Probing the Griffiths like phase, unconventional dual glassy states, giant exchange bias effects and its correlation with its electronic structure in Pr_2−x Sr _x CoMnO₆

Abstract

Electronic structure, electrical transport, dc and ac magnetization properties of the hole substituted (Sr 2+ ) partially B-site disordered double perovskite Pr 2-x Sr x CoMnO 6 system have been investigated.Electronic structure was probed by employing X-ray photoemission spectroscopy (XPS) measurements. The study suggested the presence of mixed valence states of the B-site ions (Co 2+ /Co 3+ and Mn 3+ /Mn 4+ ) with significant enhancement of the average oxidation states due to hole doping. The mere absence of electronic states near the Fermi level in the valence band (VB) spectra for both of the pure (x=0.0) and Sr doped (x=0.5) systems indicated the insulating nature of the samples. Sr substitution is observed to increase the spectral weight near the Fermi level suggesting for an enhanced conductivity of the hole doped system. The temperature variation of electrical resistivity measurements revealed the insulating nature for both the systems, thus supporting the VB spectra results. The resistivity curves were observed to follow the variable range hopping (VRH) mechanism in the entire temperature range while the analysis showed a significance enhancement in the carrier concentration due to the hole doping. The dc magnetization data divulged a Griffiths like phase above the long range ordering temperature. A typical re-entrant spin glass like phase driven by the inherent anti-site disorder (ASD) has been maidenly recognized by ac susceptibility study for both the pure and doped systems. Most interestingly, the emergence of a new cluster glass like phase (immediately below the magnetic ordering temperature and above the spin-glass transition temperature) solely driven by the Sr substitution has been unravelled by ac magnetization dynamics study. Observation of these dual glassy states in a single system is scarce and hence placed the present system amongst the rare materials. The isothermal magnetization measurements further probed the exhibition of the giant exchange bias effect emanated from the existence of multiple magnetic phases.

Griffiths phase and spontaneous exchange bias in La1.5Sr0.5CoMn0.5Fe0.5O6

“…In the case of LSCMFO, since the θ CW obtained from the CW fitting of the PM region lies far below the FM ordering T, we have chosen T R C = T C , yielding λ = 0.64. This value lies within the range found for resembling DP compounds [13,17,26,41]. The lattice distortions and the cationic disorder at the TM ionsite, intrinsic to the R 3c space group, certainly play a part in the GP.…”

“…Since the Mn 4+ ionic radius is smaller than that of Fe 3+ [16], the incorporation of Fe in the system is expected to expand the lattice, as observed. On the other hand, previous studies have also indicated a Co 2+ /Co 3+ mixed valence state in LSCMO and resembling compounds [12,15,17]. Therefore, the introduction of Fe 3+ in place of Mn 4+ induced the Co ions to a trivalent state in order to ensure the charge balance, which prevents a larger increase of the unit cell volume.…”

Enhancement of Multiferroic and Optical Properties in BiFeO3 Due to Different Exchange Interactions Between Transition and Rare Earth Ions

“…[ 65 ] Moreover, according to the Goodenough–Kanamori [ 67 ] rule, the empty Mn 3+ /Mn 4+ orbital and the full Fe 3+ /Fe 2+ orbital should have a strong FM interaction. There are different types of superexchange couplings according to the Goodenough–Kanamori rules combinations in these compounds: [ 84,85 ] 1) Mn 3+ −O 2− −Mn 3+ FM/AFM; 2) Fe 3+ −O 2− −Fe 3+ , Mn 4+ −O 2− −Mn 4+ strong AFM; 3) Fe 3+ −O 2− −Mn 3+ AFM/FM; 4) Fe 2+ −O 2− −Mn 4+ FM.…”

B-site disorder driven Griffiths-like phase and electrochemical behavior in Y2NiCrO6 double perovskite

“…In the case of ordered perovskite, the interactions between transitional metal ions are mediated by the B-O-B ′ -O-B long-range order [8,9]. Notably, at the Bsite, achieving an ordered arrangement of transition metal ions is challenging due to the presence of antisite disorder (ASD) [10,11]. This ASD is an imperfection created by interchanging the position of the transition metal ions in ordered structures [10,11].…”