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Abstract The ability to produce atomically precise, artificial oxide heterostructures allows for the possibility of producing exotic phases and enhanced susceptibilities not found in parent materials. Typical ferroelectric materials either exhibit large saturation polarization away from a phase boundary or large dielectric susceptibility near a phase boundary. Both large ferroelectric polarization and dielectric permittivity are attained wherein fully epitaxial (PbZr0.8Ti0.2O3)n/(PbZr0.4Ti0.6O3)2n(n= 2, 4, 6, 8, 16 unit cells) superlattices are produced such that the overall film chemistry is at the morphotropic phase boundary, but constitutive layers are not. Long‐ (n≥ 6) and short‐period (n= 2) superlattices reveal large ferroelectric saturation polarization (Ps= 64 µC cm−2) and small dielectric permittivity (εr≈ 400 at 10 kHz). Intermediate‐period (n= 4) superlattices, however, exhibit both large ferroelectric saturation polarization (Ps= 64 µC cm−2) and dielectric permittivity (εr= 776 at 10 kHz). First‐order reversal curve analysis reveals the presence of switching distributions for each parent layer and a third, interfacial layer wherein superlattice periodicity modulates the volume fraction of each switching distribution and thus the overall material response. This reveals that deterministic creation of artificial superlattices is an effective pathway for designing materials with enhanced responses to applied bias.
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Ferroelectric Control of Anisotropic Magnetoresistance in Ultrathin Sr 2 IrO 4 Films toward 2D Metallic Limit
Abstract The Ruddlesden‐Popper 5diridate Sr2IrO4is an antiferromagnetic Mott insulator with the electronic, magnetic, and structural properties highly intertwined. Voltage control of its magnetic state is of intense fundmenatal and technological interest but remains to be demonstrated. Here, the tuning of magnetotransport properties in 5.2 nm Sr2IrO4via interfacial ferroelectric PbZr0.2Ti0.8O3is reported. The conductance of the epitaxial PbZr0.2Ti0.8O3/Sr2IrO4heterostructure exhibits ln(T) behavior that is characteristic of 2D correlated metal, in sharp contrast to the thermally activated behavior followed by 3D variable range hopping observed in single‐layer Sr2IrO4films. Switching PbZr0.2Ti0.8O3polarization induces nonvolatile, reversible resistance modulation in Sr2IrO4. At low temperatures, the in‐plane magnetoresisance in the heterostructure transitions from positive to negative at high magnetic fields, opposite to the field dependence in single‐layer Sr2IrO4. In the polarization down state, the out‐of‐plane anisotropic magnetoresistanceRAMRexhibits sinusoidal angular dependence, with a 90° phase shift below 20 K. For the polarization up state, unusual multi‐level resistance pinning appears inRAMRbelow 30 K, pointing to enhanced magnetocrystalline anisotropy. The work sheds new light on the intriguing interplay of interface lattice coupling, charge doping, magnetoelastic effect, and possible incipient ferromagnetism in Sr2IrO4, facilitating the functional design of its electronic and material properties.
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- Award ID(s):
- 2044049
- PAR ID:
- 10589523
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Physics Research
- Volume:
- 4
- Issue:
- 8
- ISSN:
- 2751-1200
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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