Oxygen‐deficiency‐induced suppression of JT distortion and stabilization of charge ordering in La_0.2Sr_0.8MnO_3−δ

Abstract

Structural phase transition studies employing low-temperature transmission electron microscopy, and low-temperature x-ray diffraction have been carried out on nearly stoichiometric (δ=0.01) and

Evidence of ferromagnetic short-range correlations in cubic La1−xSrxMnO3−δ(x = 0.80, 0.85) above antiferromagnetic ordering

“…Our magnetic results are fully consistent with earlier reports confirming the good quality of our samples. Oxygen‐deficient samples do not show any type of long‐range ordering (structural/magnetic) as already reported .…”

“…Thus, the most robust FMC observed in our samples as compared to earlier reports on distorted perovskite manganites, indicates the strengthening of short-range FMC by its favorable highly symmetric cubic lattice. In our case, the oxygen stoichiometric samples show a magnetostructural phase transition [37,38] whereas nonstoichiometric ones remain cubic down to low temperature, but their magnetization, T FMC and T Ã remain nearly the same, thus this does not support the Turcaud et al [28] model for low-temperature (high magnetic field) phase. In manganites, a broken magnetic Mn-O-Mn network in perovskite lattice is expected to cause drastic effect on FMC if it is caused by the GP-like singularity.…”

“…The oxygen off‐stoichiometric samples show similar χ −1 ( T ) behavior as that of stoichiometric ones with only a few Kelvin shifts in T FMC accompanied by the weakening of AFM correlations. These observations illustrate that although oxygen vacancies completely destroy the coupled low‐ T structural and magnetic phase transition it does not have any major effect on T *, T FMC , and the strength of FMC.…”

“…3 Results and discussion Figure 1a-d represents the low-field (100 Oe) and high-field (50, 70 kOe) M(T) behavior in ZFC and FC modes. It shows a clear cusp around T N $ 238 K and $260 K for oxygen stoichiometric La 0.15 Sr 0.85 MnO 2.98 and La 0.20 Sr 0.80 MnO 2.99 samples, respectively, associated with the onset of long-range C-type canted AFM spin ordering [33,34] concomitant with cubic to tetragonal structural transitions [37,38]. In the case of La 0.15 Sr 0.85 MnO 2.98 , in addition to T N , there is another anomaly around 100 K, whose origin is still unclear.…”

“…In all these previous reports the magnetic studies have been done maximum up to 400 K [32][33][34] at single H with prime interest to know the AFM ordering temperature (T N ). Recently, we have studied the effect of oxygen vacancies in these compounds and observed that the oxygen vacancies completely suppress the coupled structural, magnetic and electronic phase transitions 37,38 . We have observed that oxygen vacancies actually stabilize the above reported charge ordered phase in a cubic perovskite lattice 37 .…”