Ferroelectric capped magnetization in multiferroic PZT/LSMO tunnel junctions

Abstract

Self-poled ultra-thin ferroelectric PbZr 0.52 Ti 0.48 O 3 (PZT) (5 and 7 nm) films have been grown by pulsed laser deposition technique on ferromagnetic La 0.67 Sr 0.33 MnO 3 (LSMO) (30 nm) to check the effect of polar capping on magnetization for ferroelectric tunnel junction (FTJ) devices.PZT/LSMO heterostructures with thick polar PZT (7 nm) capping show nearly 100% enhancement in magnetization compared with thin polar PZT (5 nm) films, probably due to excess hole transfer from the ferroelectric to the ferromagnetic layers. Core-level X-ray photoelectron spectroscopy studies revealed the presence of larger Mn 3s exchange splitting and higher Mn 3+ /Mn 4+ ion ratio in the LMSO with 7 nm polar capping.

Low‐Pressure Mechanical Switching of Ferroelectric Domains in PbZr0.48Ti0.52O3

“…In PZT films below 8 nm, the as-grown polarization direction is "up" (i.e., pointing out of the surface), while it is pointing "down" for the 10 nm film (S3). A reversal of as-grown polarization direction dependent on film thickness has also been found in other reports on ferroelectric heterostructures, including MPB members of Pb(Zr x Ti (1−x) )O 3 [28,32] and BFO. [36,37] In these reports, the reversal is explained by a competition between a flexoelectric effect induced by the strain in the film and an electric field due to band bending at the interface.…”

“…[1 ] In a related attempt Edwards et al [6] reported the mechanical switching threshold (1000 nN: estimated tip pressure = 0.8 GPa; tip radius = 20 nm) of polycrystalline PbZr 0.53 Ti 0.47 O 3 , which lays at the morphotropic phase boundary (MPB) of the Pb(Zr x Ti (1−x) )O 3 family. Compositions close to the MPB of Pb(Zr x Ti (1−x) )O 3 offer the possibility of transitions between tetragonal and rhombohedral phases due to small strains [27][28][29][30][31] as well as the co-existence of tetragonal and rhombohedral phases, [5,32] and have been investigated with respect to thickness-dependent flexoelectric fields, [32] making them ideal for pressure-induced polarization switching. Therefore, in this work, we explore the ferroelectric and mechanical Figure 1a shows the room temperature (297 K) HR-X-ray diffraction (XRD) patterns of the PZT/YBCO/LAO heterostructures.…”

Experimental evidence of electronic polarization in a family of photo-ferroelectrics

“…The binding energy difference between the spin-orbit peaks is about 5.4 eV suggests that Bi is in a single valence state with Bi 3+ ion valency. [50][51][52] A broad and diffused Ti 2p 3/2 peak is obtained near 457.8 eV suggests most of the Ti cations are in +4 states. The Zr 3d 5/2 and 3d 3/2 illustrate well dened peaks located at $181.5 eV and $183.9 eV, respectively with a weak hump near 180 eV.…”

Magnetocaloric effect and piezoresponse of engineered ferroelectric-ferromagnetic heterostructures

“…These transitions can be tuned using chromium (Cr) and titanium (Ti) substitution at temperatures of 326 K and 210 K, respectively [27]. The change in the thickness of LSMO layer can also act to tune of these transition temperatures [28]. Compositional and configurational tuning also leads to variation in magnetization dependant heat capacity which further affects its magnetocaloric cooling capacity; as an example, the magnetization dependent change in heat capacity (∆CP (T, µ0H)=CP (T, µ0H) -CP (T, 0)) of Ti-substituted LSMO ranges for 6.2 to -4.2 Jkg -1 K -1 while for Cr substituted compositions it lies in the range of 21 to -11 Jkg -1 K -1 [27].…”