ESR Studies on ${\rm Bi}_{0.5}{\rm Ca}_{0.5}{\rm Mn}_{0.95}{\rm TE}_{0.05}{\rm O}_{3}$ (${\rm TE}={\rm V}$, Cu and Zn)

Abstract

In this work, the effect of transition element ( TE=V, Cu, and Zn) substitution at Mn site on the electron spin resonance (ESR) of Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> Ca <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> MnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> was explored. The temperature (T) dependent double integrated intensity (DI) and peak to peak linewidth provide the estimation of charge ordering (CO) temperature T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CO</sub> , long-range antiferromagnetic (AFM) onset temperature, T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O</sub> , ordering temperature, T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</sub> , and the information about the magnetic interactions. The T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CO</sub> values are 317 K, 317 K, 321 K, and 311 K for undoped, V, Cu, and Zn doped samples, respectively. It is noticed that V doping sharpens the CO transition, whereas Cu and Zn doping smears the CO transition. The temperature dependent magnetization measurements support the ESR observations. In the temperature range T >; T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CO</sub> , ferromagnetic (FM) correlations dominate. In the temperature range T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CO</sub> >; T >; T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O</sub> , the samples are in the paramagnetic (PM+CO) phase. The AFM interactions dominate in the doped samples in this temperature range. The orbital ordering (OO) sets in progressively with decreasing temperature leading to onset of long-range AFM ordering at ~ 200 K for undoped and in the range 190-170 K for doped samples. The present study shows the strong competition between FM and AFM correlations as a function of temperature and composition of the sample.