Novel photoinduced phase transitions in transition metal oxides and diluted magnetic semiconductors

Abstract

Some transition metal oxides have frustrated electronic states under multiphase competition due to strongly correlated d electrons with spin, charge, and orbital degrees of freedom and exhibit drastic responses to external stimuli such as optical excitation. Here, we present photoemission studies on Pr0.55(Ca1 − ySry)0.45MnO3 (y = 0.25), SrTiO3, and Ti1 − xCoxO2 (x = 0.05, 0.10) under laser illumination and discuss electronic structural changes induced by optical excitation in these strongly correlated oxides. We discuss the novel photoinduced phase transitions in these transition metal oxides and diluted magnetic semiconductors on the basis of polaronic pictures such as orbital, ferromagnetic, and ferroelectric polarons.

Local bias induced ferroelectricity in manganites with competing charge and orbital order states

“…The highly confined electric field and a partial injection and trapping of charge carriers can reorganize the local polaronic distribution (modulated strain/electron/spin), 21 usually found in thermodynamic disarray at room temperature, hence promoting the expansion of a particular metastable state which can be detected by a dielectric/ferroelectric signature in contrast to the electrical properties of the conventional host phase. [22][23][24] The formation of these embedded charge/orbital and antiferromagnetic orders prevent electron hopping, and the correlations can survive locally as ''Zener polarons'' 25,26 above T CO and even T N . Under these circumstances Mn ions and Mn-O-Mn bonds become nonequivalent resulting in a noncentrosymmetric electronic structure which is prone to exhibit some piezoelectric response.…”

Structure of Vanadium-Doped Zinc Oxide, Zn1–XVxO

“…After the report by Ueda et al [9] that semiconductor ZnO exhibits room temperature ferromagnetism when some atomic percentage of transition metal ions was doped, the study on zinc oxide-based DMS gained importance. DMS materials when grown with transition metal ions prevail electric and magnetic properties for the reason that transition metal d electrons correlates with spin, charge, and orbital degrees of freedom [10]. The behavior of transition metal doped on high k dilute magnetic oxides exhibiting room temperature ferromagnetism paving way to realize hybrid spintronic devices [11].…”