Ni-doped La_0.5Sr_0.5TiO₃ nanofibers: Fabrication and intrinsic ferromagnetism

<jats:title>Abstract</jats:title> <jats:p>We report room-temperature ferromagnetism in ∼104–133 nm nanofibers of La<jats:sub>0.5</jats:sub>Sr<jats:sub>0.5</jats:sub>Ti<jats:sub>1−</jats:sub> <jats:italic> <jats:sub>x</jats:sub> </jats:italic>Ni<jats:italic> <jats:sub>x</jats:sub> </jats:italic>O<jats:sub>3</jats:sub> (0.02 ≤ <jats:italic>x</jats:italic> ≤ 0.05). As-spun nanofibers of La<jats:sub>0.5</jats:sub>Sr<jats:sub>0.5</jats:sub>Ti<jats:sub>1−</jats:sub> <jats:italic> <jats:sub>x</jats:sub> </jats:italic>Ni<jats:italic> <jats:sub>x</jats:sub> </jats:italic>O<jats:sub>3</jats:sub> are fabricated by an electrospinning technique. Nanofibers of the as spun and calcined La<jats:sub>0.5</jats:sub>Sr<jats:sub>0.5</jats:sub>Ti<jats:sub>1−</jats:sub> <jats:italic> <jats:sub>x</jats:sub> </jats:italic>Ni<jats:italic> <jats:sub>x</jats:sub> </jats:italic>O<jats:sub>3</jats:sub> samples are characterized using X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), X-ray photoelectron microscopy (XPS), X-ray absorption near edge structure (XANES) determination, and vibrating sample magnetometry (VSM). The results of XRD analysis and TEM together with selected electron diffraction (SEAD) analysis indicate that La<jats:sub>0.5</jats:sub>Sr<jats:sub>0.5</jats:sub>Ti<jats:sub>1−</jats:sub> <jats:italic> <jats:sub>x</jats:sub> </jats:italic>Ni<jats:italic> <jats:sub>x</jats:sub> </jats:italic>O<jats:sub>3</jats:sub> nanofibers have a cubic perovskite structure with no secondary phase. The as-spun samples are paramagnetic, whereas the La<jats:sub>0.5</jats:sub>Sr<jats:sub>0.5</jats:sub>Ti<jats:sub>1−</jats:sub> <jats:italic> <jats:sub>x</jats:sub> </jats:italic>Ni<jats:italic> <jats:sub>x</jats:sub> </jats:italic>O<jats:sub>3</jats:sub> samples are ferromagnetic having specific magnetizations of 0.098–0.484 emu/g at 10 kOe. The XPS spectra show that there are some oxygen vacancies in the nanofibers, which its may play an important role in inducing room-temperature ferromagnetism in La<jats:sub>0.5</jats:sub>Sr<jats:sub>0.5</jats:sub>Ti<jats:sub>1−</jats:sub> <jats:italic> <jats:sub>x</jats:sub> </jats:italic>Ni<jats:italic> <jats:sub>x</jats:sub> </jats:italic>O<jats:sub>3</jats:sub> nanofibers. XANES spectra show that most of the Ni ions in La<jats:sub>0.5</jats:sub>Sr<jats:sub>0.5</jats:sub>Ti<jats:sub>1−</jats:sub> <jats:italic> <jats:sub>x</jats:sub> </jats:italic>Ni<jats:italic> <jats:sub>x</jats:sub> </jats:italic>O<jats:sub>3</jats:sub> nanofibers are in the Ni<jats:sup>2+</jats:sup> state mixed with some Ni metal. The finding of room temperature ferromagnetism in this nanofibrous structure of the La<jats:sub>0.5</jats:sub>Sr<jats:sub>0.5</jats:sub>Ti<jats:sub>1−</jats:sub> <jats:italic> <jats:sub>x</jats:sub> </jats:italic>Ni<jats:italic> <jats:sub>x</jats:sub> </jats:italic>O<jats:sub>3</jats:sub> system is of interest in research on diluted magnetic oxides.</jats:p>