A new approach to prepare surface-functionalized magnetic nanoparticles by synthesis of poly(methacrylic acid) (PMAA) coated maghemite nanoparticles in aqueous solution is reported. Maghemite (c-Fe 2 O 3 ) nanoparticles with an average diameter of 8 ¡ 2 nm were fabricated and subsequently coated with PMAA by emulsion polymerization. The FTIR study and thermal analysis confirmed the chemical adsorption of methacrylic acid on the maghemite nanoparticle surface, and suggested a symmetrical carboxylate bonding. The free carboxyl group of PMAA, which was verified by FTIR spectroscopy and zeta potential measurement, provided the site for immobilization of foreign molecules. The PMAA coated maghemite nanoparticles were demonstrated as potential magnetically targeted drug carriers by adsorbing an anti-cancer drug (carboplatin) via the ion-dipole interaction between CO 2 2 of PMAA and carboplatin.

Topological Hall effect (THE), appearing as bumps and/or dips in the Hall resistance curves, is considered as a hallmark of the skyrmion spin texture originated from the inversion symmetry breaking and spin–orbit interaction. Recently, Néel‐type skyrmion is proposed based on the observed THE in 5d transition metal oxides heterostructures such as SrRuO3/SrIrO3 bilayers, where the interfacial Dzyaloshinskii–Moriya interaction (DMI), due to the strong spin–orbit coupling (SOC) in SrIrO3 and the broken inversion symmetry at the interface, is believed to play a significant role. Here the emergence of THE in SrRuO3 single layers with thickness ranging from 3 to 6 nm is experimentally demonstrated. It is found that the oxygen octahedron rotation in SrRuO3 also has a significant effect on the observed THE. Furthermore, the THE may be continuously tuned by an applied electrical field. It is proposed that the large SOC of Ru ions together with the broken inversion symmetry, mainly from the interface, produce the DMI that is responsible for the observed THE. The emergence of the gate‐tunable DMI in SrRuO3 single layer may stimulate further investigations of new spin–orbit physics in strong SOC oxides.

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