Magnetic Ordering in Sr3YCo4O10+x

Abstract

Transition-metal oxides often exhibit complex magnetic behavior due to the strong interplay between atomic-structure, electronic and magnetic degrees of freedom. Cobaltates, especially, exhibit complex behavior because of cobalt’s ability to adopt various valence and spin state configurations. The case of the oxygen-deficient perovskite Sr3YCo4O10+x (SYCO) has attracted considerable attention because of persisting uncertainties about its structure and the origin of the observed room temperature ferromagnetism. Here we report a combined investigation of SYCO using aberration-corrected scanning transmission electron microscopy and density functional theory calculations. Guided by theoretical results on Co-O distances projected on different planes, the atomic-scale images of several different orientations, especially of the fully oxygenated planes, allow the unambiguous extraction of the underlying structure. The calculated magnetic properties of the new structure are in excellent agreement with the experimental data.

Room temperature magnetoresistance and exchange bias in “314-type” oxygen-vacancy ordered SrCo0.85Fe0.15O2.62

“…There are two different Co sites in this layered structure, one is oxygen-replete (Co2/Fe2, see figure 1) and another oxygen-deficient (Co1/Fe1). As mentioned previously [14][15][16] , the ferrimagnetic structure is formed with a Co 3+ high -spin (HS, t 4 2g e 2 g , S = 2) state and intermediate-spin (IS, t 5 2g e 1 g , S = 1) state ordering (AFM aligned) in the oxygen-replete layers, while the Co cations in the oxygen deficient site are nearly compensated. Therefore, the large EB effect in this sample can be attributed to the coexistence of nearly compensated and ferrimagnetic regions.…”

“…The oxygen deficient "314-type" compounds crystallize in a tetragonal symmetry, space group I4/mmm with a 2a p × 2a p × 4a p (a p = lattice parameter of the cubic perovskite) type unit cell and show the appearance of above RT ferrimagnetism. [11][12][13][14][15][16] A pure phase polycrystalline sample of SrCo 0.85 Fe 0.15 O 2.62 was prepared by standard solid-state reaction method as reported previously. 16 The sample was characterized by X-ray powder diffraction (XRD) at room temperature (RT), performed in a Panalytical a) soumarik@gmail.com b) rpsingh@iiserb.ac.in X'pert Pro diffractometer (Cu K α radiation, λ = 1.5406 Å).…”

Moderate magnetic field induced large exchange bias effect in ferrimagnetic 314—Sr3YCo4O10.5material

“…A pure phase polycrystalline sample of Sr 3 YCo 4 O 10.5 was prepared by the standard solid-state reaction as reported earlier [17,18].…”

“…1) type unit cell and shows the appearance of ferrimagnetism well above RT. In this compound Co 3+ cations in the oxygen replete layers are antiferromagnetically aligned with alternating high -spin (HS, t 2g 4 e g 2 , S = 2) state and intermediate -spin (IS, t 2g 5 e g 1 , S = 1) state, resulting in above RT ferrimagnetism [17,18,19].…”

Ferromagnet-antiferromagnet transition in layered perovskites of Sr3YCo4O10.5 type

“…A number of scenarios for the appearance of the ferromagnetic component have been described: for example, orbital ordering in Co 3+ (IS) ions located in oxygen-stoichiometric CoO 6 layers is proposed as the reason for ferrimagneticcomponent [11,12],ferrimagnetic structure in anion deficient layers due to oxygen vacancies ordering [13], Ferromagnetic Co 3+ chains in oxygen-stoichiometric CoO 6 layers [14], spin "bags" in CoO 6 layers [15] and a uncompensated canted magnetic structure [16]. The questions are still actually: whether or not the magnetic ordering is accompanied by a structural transition [11][12] andcrystal structureimpact on stability of ferromagnetic component.…”