Antisite disorder driven spontaneous exchange bias effect in La_2−xSr_xCoMnO₆(0  ⩽  x  ⩽  1)

Abstract

Doping at the rare-earth site by divalent alkaline-earth ions in perovskite lattice has witnessed a variety of magnetic and electronic orders with spatially correlated charge, spin and orbital degrees of freedom. Here, we report an antisite disorder driven spontaneous exchange bias effect as a result of hole carrier (Sr(2+)) doping in La(2-x)Sr(x)CoMnO6 (0 < x < 1) double perovskites. X-ray diffraction and Raman spectroscopy have evidenced an increase in disorder with the increase of Sr content up to x = 0.5 and thereby a decrease from x = 0.5 to 1. X-ray absorption spectroscopy has revealed that only Co is present in the mixed valence of Co(2+) and Co(3+) states with Sr doping to compensate the charge neutrality. Magnetotransport is strongly correlated with the increase of antisite disorder. The antisite disorder at the B-site interrupts the long-range ferromagnetic order by introducing various magnetic interactions and instigates reentrant glassy dynamics, phase separation and canted type antiferromagnetic behavior with the decrease of temperature. This leads to a novel magnetic microstructure with unidirectional anisotropy that causes a spontaneous exchange bias effect that can be tuned with the amount of antisite disorder.

Different oxidation routes for lattice oxygen recovery of double-perovskite type oxides LaSrFeCoO 6 as oxygen carriers for chemical looping steam methane reforming

“…But antisite defects always exist in reality, causing a certain degree of Fe/Co disorder, and consequently leading to the generation of impurity phase. The existence of antisite disorder is inevitable in the double perovskite structure and plays a vital role in their physical properties [25] . Fig.…”

Absence of zero-field-cooled exchange bias effect in single crystalline La2−xAx CoMnO6 Macchiutti1, Jesus2, Carneiro3 et al. 2021Phys. Rev. Materials

“…We see no hysteresis loop shifts, i.e., no ZEB effect for LCCMO and LSCMO single crystals (see the right side inset of Fig. 5), in contrast to what was observed in polycrystals [2][3][4][5]7,9]. Also, we do not observe the conventional EB effect after FC at H = 9 T for all samples (not shown).…”

“…There is great interest in this family of compounds due to the possible applications in spintronic devices. Particularly interesting is the zero-field-cooled (ZFC) exchange bias (ZEB) effect recently observed for hole-doped members of this family of compounds [2][3][4][5][6][7][8][9]. The conventional exchange bias (CEB) effect is characterized as a shift in hysteresis loop measurements, observed after cooling the system in the presence of an external magnetic field [10].…”

“…The conventional exchange bias (CEB) effect is characterized as a shift in hysteresis loop measurements, observed after cooling the system in the presence of an external magnetic field [10]. In materials in which the ZEB effect is seen, the shift in magnetization as a function of the applied field is detected spontaneously in zero-field cooling [2][3][4][5][6][7][8][9]. In these double perovskites, the ZEB effect may result from a reentrant spin-glass-like phase in which magnetic relaxation of unusual glassy moments affects the magnetization loop shifts [11,12].…”

“…For La 1.5 Ca 0.5 CoMnO 6 (LCCMO) and La 1.5 Sr 0.5 CoMnO 6 (LSCMO) materials, it has been reported in polycrystalline samples that by substituting the La 3+ cation by 25% of an alkaline-earth ion with 2+ valence, gives rise to a spin-glass phase which promotes the unusual ZEB effect [2,3,5,7,11,12]. It was also shown that Ba doping can tune the ZEB effect in LSCMO [21].…”