Novel Dynamical Effects and Glassy Response in a Strongly Correlated Electronic System

Abstract

We find an unconventional nucleation of low temperature paramagnetic metal (PMM) phase with monoclinic structure from the matrix of high-temperature antiferromagnetic insulator (AFI) phase with tetragonal structure in strongly correlated electronic system BaCo0.9N i0.1S1.97. Such unconventional nucleation leads to a decease in resistivity by several orders with relaxation at a fixed temperature without external perturbation. The novel dynamical process could arise from the competition of strain fields, Coulomb interactions, magnetic correlations and disorders. Such competition may frustrate the nucleation, giving rise to a slow, nonexponential relaxation and "physical aging" behavior. [3,4]. Such nonergodic behavior is very interesting because one normally expects electron systems to relax rather rapidly. Many glassy systems exhibit a nonstationary behavior that has been described as "physical aging" [5]. Recently, the electron glass has received renewed interest [6,7] as the subject of electron-electron interactions has become a central topic in understanding the metal-insulator transition (MIT) in two dimensions [8]. Such glass behavior is believed to be associated with the interplay between disorder and strong electronic correlations [9]. Phase separation widely observed in strongly correlated electronic system [10,11] provides the possibility for appearance of locally metastable states, giving rise to the self-organized inhomogeneities (disorders). Phase separation (PS) scenario appears as particularly favorable for the existence of out-of-equilibrium features. Therefore, it is expected that the glass behavior occurs in the strongly correlated electronic system due to interplay between disorder and strong electronic correlations [9], especially in phase separation region. Indeed, a pronounced glassy response [12] and a memory effect have been recently observed in phase separated manganites [13]. The interplay of strong electronic correlations and disorder is believed to be responsible for many new phenomena occurring in complex materials in the MIT region [14]. Therefore, Novel findings in complex materials with strongly electronic correlations in the MIT region clearly deserves further study.BaCoS 2 is a Mott-Hubbard insulator having Co 2 S 2 layers with spin-1/2 Co ions that order antiferomagnetically at 310 K, and properties shared by members of the high T c cuprates. Such quasi-two dimensional system BaCoS 2 with CoS conducting planes separated by insulating BaS rocksalt sheets is structurally analogous to the high-T c cuprates [15]. Substitution of Ni for Co leads to a first-order transition from an antiferromagnetic insulator (AFI) to a paramagnetic metal (PMM) upon cooling at T c in the layered BaCo 0.9 N i 0.1 S 2−y system for 0.05 ≤ y ≤ 0.20 [15]. Such AFI-PMM phase transition is associated with a structural change from hightemperature tetragonal (HTT) phase to low-temperature monoclinic (LTM) phase [16].In this letter, we report a novel dynamical process for the MIT transition due to the interplay...

Real-space visualization of thermomagnetic irreversibility within supercooling and superheating spinodals inMn1.85Co0.15Sbusing scanning Hall probe microscopy

“…This broadening gives rise to coexistence of competing phases in the transition region. The metastability of coexisting phases within (and below) the supercooling and superheating spinodals has been of wide interest and actively pursued in a wide variety of systems like systems showing metal insulator transitions 2,3,4 , multiferroics 5 , intermetallics 6 etc. The understanding of magnetic first order transition (due to easy control of magnetic field (H) and temperature (T) ) also has implication to wider class of systems where first order transition plays a role (like glass transition where pressure and quenching rate are sometimes difficult to control).…”