Electric-Field Reversible Switching of the Exchange Spring and Exchange Bias Effect in SrCoO_3–x/La_0.7Sr_0.3MnO₃ Heterostructures

Abstract

The technique of electrical field to manipulate physicochemical properties of oxide heterostructures has ample potential in electronic and ionitronic devices. SrCoO 3−x is a famous "sponge" material displaying topotactic structural phase transition from perovskite (0 ≤ x ≤ 0.25) to brownmillerite (x = 0.5) accompanied by the magnetic phase transition from ferromagnetism to antiferromagnetism, which can be controlled reversibly by electric field via the ionic liquid gating method. Here, the exchange spring effect can be observed at the perovskite SrCoO 3−x (P-SCO)/La 0.7 Sr 0.3 MnO 3 (LSMO) bilayer, while the exchange bias effect is received at the brownmillerite SrCoO 2.5 (B-SCO)/LSMO bilayer. The reversible and nonvolatile switching of the exchange spring and exchange bias effect can be achieved in these SCO 3−x /LSMO bilayers by utilizing ionic liquid gating to control the annihilation or generation of oxygen vacancies. In addition, the variations in the stacking orders of these SCO 3−x /LSMO bilayers are investigated because the previous SCO 3−x layer always acts as the cover layer. It is worth noting that LSMO/SCO 3−x bilayer magnetization is strongly suppressed when the SCO 3−x layer is used as the bottom layer. Combined with the X-ray line dichroism measurements, it is suggested that the bottom SCO 3−x layer would induce the spin arrangements in the LSMO layer to have the tendency toward the out-of-plane orientation. This is the reason for the sharp decrease in magnetization of LSMO/SCO 3−x bilayers. Our investigations accomplish a reversible control of the exchange coupling transition in all-oxide bilayers and provide the foundation for further electric-field control of magnetic properties.

Electric field-controlled reversible high-temperature perpendicular magnetic anisotropy in cobaltate–manganite heterostructures

“…In addition, the IP M-H curve of the P-SCO/LSMO bilayer exhibits a peculiar wasp-waisted shape due to the interface exchange spring effect. According to reported works, the M-H curve can be further decomposed into two independent magnetic hysteresis loops: 21,39 the wasp-waist shape generated from the LSMO layer with a small coercivity force and the two bellies related to the P-SCO layer. Consequently, the LSMO layer in the bilayer structure retains its IP magnetic anisotropy, and the result is in agreement with that of LSMO single films.…”

“…Due to the discrepancy in the formation energies of oxygen vacancies between the LSMO and B-SCO layers, it is possible to just influence the top B-SCO layer while ensuring that the bottom LSMO is unaffected by applying an appropriate bias voltage on the bilayer. 21,28,30 When a negative voltage is applied, the oxygen ions are inserted into the films, causing B-SCO to transition to the P-SCO state. On the contrary, the application of a positive electric field on the same sample can attract the oxygen ions and create oxygen vacancies in the films while the top B-SCO layer is recovered.…”

“…[14][15][16][17] Currently, the development of strategies to electrically control the magnetic properties of materials by ionic-liquid-gating (ILG) is gaining momentum. 14,[18][19][20][21] An electric double-layer can be formed during the process of gating, which produces a large electric field in the opposite direction of other electric-control methods. Natural oxygen sponge-like materials such as brownmillerite SrCoO 2.5 (B-SCO), composed of alternating CoO 4 tetrahedral and CoO 6 octahedral layers, are promising materials for ion migration driven by an electric field due to their onedimensional oxygen vacancy channels.…”

“…[26][27][28] Moreover, in previous reports, the anomalous magnetic behavior has been tuned at brownmillerite-based heterostructures by the electric field. 21,[28][29][30] In this paper, first-principles calculations reveal that LSMO film combined with a B-SCO layer can exhibit PMA. Based on this, (001)orientated B-SCO/LSMO bilayers have been fabricated on the tensile strain STO substrate.…”

Modulation of Exchange Bias in La0.35Sr0.65MnO3/La0.7Sr0.3MnO3 through Volatile Polarization of P(VDF‐TrFE) Gate Dielectric

“…Breakthroughs along this direction have been made based on magnetoelectric coupling effect in AF insulators, [14][15][16] ferroelectric polarization in ferroelectric/FM heterostructures, [17,18] and electrochemical reactions in magnetoionic devices. [19][20][21][22][23] Ferroelectric copolymer of polyvinylidene fluoride with trifluoroethylene (P(VDF-TrFE)) has been widely used in organic field effect transistors (FET). [24] Meanwhile, reports on utilizing In typical ferroelectric field effect devices, the application of V a across the ferroelectric layer leads to certain polarization (highlighted as "I" in lower panel).…”