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Abstract Exchange bias (EB), manifested as a hysteresis‐loop offset after field‐cooling, is demonstrated in perovskite‐structured ferromagnet/antiferromagnet (La_0.67Sr_0.33MnO₃/YFeO₃)_nheterostructures grown on (100) SrTiO₃substrates. Bilayer samples show an EB of 306 Oe at 50 K, whereas multilayers with five layers exhibit an exchange bias of up to 424 Oe at 50 K. A spin valve consisting of La_0.67Sr_0.33MnO₃/SrTiO₃/La_0.67Sr_0.33MnO₃/YFeO₃shows stable remanent configurations resulting from pinning of the upper La_0.67Sr_0.33MnO₃layer by the YFeO₃. In contrast, EB is not observed on (111)‐oriented SrTiO₃substrates due to interface roughening. These results demonstrate YFeO₃as an alternative orthoferrite antiferromagnet compared to BiFeO₃and LaFeO₃for incorporation into exchange‐biased heterostructures. 

Elementary science education, particularly in the 4th and 5th grades, is essential for setting the foundation for lifelong science learning, fostering critical thinking, and preparing students for success in science, technology, engineering, and mathematics (STEM) fields. This stage is especially critical for students with disabilities, as achievement gaps between them and their peers emerge during elementary school. Despite this importance, little is known about how science is taught in elementary classrooms during these critical years, particularly for students with disabilities. To address this gap, we surveyed teachers from a nationally representative sample of U.S. schools to examine elementary science education, including instructional practices, allocation of time, and the inclusion and support of students with disabilities. Our findings reveal that limited instructional time is allocated to science, with significant variability across classrooms. The amount of time dedicated to science instruction was significantly influenced by external factors, such as whether science was a tested subject. Students with disabilities often face additional barriers, including being pulled out of science instruction for special education services, resulting in missed opportunities to engage in science. These findings highlight the need to address opportunity gaps in science instruction to ensure all students have meaningful access to quality science education. 

Abstract Oxygen coordination and vacancy ordering play an important role in dictating the functionality of complex oxides. In this work, an unconventional layering of oxygen ions in a mixed conductor SrCo_1‐xFe_xO_3‐δ(SCFO) thin film grown epitaxially on SrTiO₃(STO) is reported. Scanning transmission electron microscopy (STEM) reveals alternating layers of oxygen deficiency along the growth direction, with the oxygen‐rich layer correlated with the neighboring Co,Fe‐site intensity, and contraction of the Sr–Sr distance. Density functional theory (DFT) calculations and STEM image simulations support the emergence of periodic (Co,Fe)O₆and (Co,Fe)O₄/(Co,Fe)O₅layers, an ordering that is also sensitive to the Co:Fe ratio. 

Abstract Single-phase multiferroic materials that allow the coexistence of ferroelectric and magnetic ordering above room temperature are highly desirable, motivating an ongoing search for mechanisms for unconventional ferroelectricity in magnetic oxides. Here, we report an antisite defect mechanism for room temperature ferroelectricity in epitaxial thin films of yttrium orthoferrite, YFeO 3 , a perovskite-structured canted antiferromagnet. A combination of piezoresponse force microscopy, atomically resolved elemental mapping with aberration corrected scanning transmission electron microscopy and density functional theory calculations reveals that the presence of Y Fe antisite defects facilitates a non-centrosymmetric distortion promoting ferroelectricity. This mechanism is predicted to work analogously for other rare earth orthoferrites, with a dependence of the polarization on the radius of the rare earth cation. Our work uncovers the distinctive role of antisite defects in providing a mechanism for ferroelectricity in a range of magnetic orthoferrites and further augments the functionality of this family of complex oxides for multiferroic applications. 

Abstract This work characterizes the structural, magnetic, and ferroelectric properties of epitaxial LuFeO₃orthoferrite thin films with different Lu/Fe ratios. LuFeO₃thin films are grown by pulsed laser deposition on SrTiO₃substrates with Lu/Fe ratio ranging from 0.6 to 1.5. LuFeO₃is antiferromagnetic with a weak canted moment perpendicular to the film plane. Piezoresponse force microscopy imaging and switching spectroscopy reveal room temperature ferroelectricity in Lu‐rich and Fe‐rich films, whereas the stoichiometric film shows little polarization. Ferroelectricity in Lu‐rich films is present for a range of deposition conditions and crystallographic orientations. Positive‐up‐negative‐down ferroelectric measurements on a Lu‐rich film yield ≈13 µC cm⁻²of switchable polarization, although the film also shows electrical leakage. The ferroelectric response is attributed to antisite defects analogous to that of Y‐rich YFeO₃, yielding multiferroicity via defect engineering in a rare earth orthoferrite. 

Abstract Complex oxide films stabilized by epitaxial growth can exhibit large populations of point defects which have important effects on their properties. The site occupancy of pulsed laser‐deposited epitaxial terbium iron garnet (TbIG) films with excess terbium (Tb) is analyzed, in which the terbium:iron (Tb:Fe)ratio is 0.86 compared to the stoichiometric value of 0.6. The magnetic properties of the TbIG are sensitive to site occupancy, exhibiting a higher compensation temperature (by 90 K) and a lower Curie temperature (by 40 K) than the bulk Tb₃Fe₅O₁₂garnet. Data derived from X‐ray core‐level spectroscopy, magnetometry, and molecular field coefficient modeling are consistent with occupancy of the dodecahedral sites by Tb³⁺, the octahedral sites by Fe³⁺, Tb³⁺and vacancies, and the tetrahedral sites by Fe³⁺and vacancies. Energy dispersive X‐ray spectroscopy in a scanning transmission electron microscope provides direct evidence of Tb_Feantisites. A small fraction of Fe²⁺is present, and oxygen vacancies are inferred to be present to maintain charge neutrality. Variation of the site occupancies provides a path to considerable manipulation of the magnetic properties of epitaxial iron garnet films and other complex oxides, which readily accommodate stoichiometries not found in their bulk counterparts.