Effect of oxygen off-stoichiometry on coupled structural and magnetic phase-transitions in La0.15Sr0.85MnO3−δ (δ=0.02, 0.14)

Abstract

Effect of oxygen off-stoichiometry on the structural and magnetic properties of La 0.15 Sr 0.85 MnO 3−δ (δ=0.02, 0.14) has been studied employing low-temperature x-ray diffraction, calorimetry, electricaltransport and magnetization. The nearly stoichiometric composition under goes first order phasetransition from cubic to tetragonal P4/mmm at 238K accompanied by magnetic and electrical phasetransitions. On the contrary the off-stoichiometric composition does not show any transition and remain cubic Pm-3m down to 80K. Off-stoichiometry induced oxygen-vacancy seems to suppress the cooperative JT distortion and possibly stabilize a G-type antiferromagnetic phase with localized cantedspins. Thus we demonstrate that controlling oxygen stoichiometry is a way of structure/property engineering in electron doped like manganites.

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.…”

Influence of Grinding Particle Size on Structure and Electrical Properties of La0.67Sr0.33MnO3−δCompound

“…It can be manipulated by cation doping, says strontium in our case, into the La-site of LaMnO3 or by oxygen deficiency through processing material in gas medium 8 [19]. In our work, since the size controlling was performed by mechanical grinding, the compound possibly lost the oxygen during the grinding process [8,16], and therefore, the contribution of Mn 4+ content should be taken into account.…”