AI 中文总结
研究镍基尖晶石氧化物NiCo2O4，发现其在外部磁场冷却时有交换偏置效应，5K时交换偏置场约375 Oe，10K时负磁阻约31.5%。经分析，负磁阻和交换偏置现象源于反相边界形成，由高分辨率透射电子显微镜证实。
AI 中文摘要
镍基尖晶石氧化物因其显著的磁输运特性最近备受关注，有望用于各种自旋电子应用。本研究中，当单相纳米晶NiCo2O4在外部磁场中冷却时，观察到交换偏置效应，磁滞回线会水平和垂直移动。5K时交换偏置场大小约为375 Oe，300K左右消失。此外，NiCo2O4在纵向电阻率中表现出半导体行为，10K时负磁阻约为31.5%，低磁场下磁阻呈蝶形，高磁场下近似线性。对负磁阻和交换偏置的详细分析表明，这两种现象均源于合成的NiCo2O4样品中反相边界的形成，高分辨率透射电子显微镜证实了这一点。
英文摘要
Nickel-based spinel oxide has recently attracted significant attention due to its remarkable magneto-transport properties, promising various spintronic applications. In this study, we observe an exchange bias effect, where the magnetic hysteresis loop shifts both horizontally and vertically when single-phase nanocrystalline NiCo2O4 is cooled in the presence of an external magnetic field. The magnitude of the exchange bias field is approximately 375 Oe at 5 K, and this effect disappears around 300 K. Furthermore, NiCo2O4 shows semiconducting behaviour in longitudinal resistivity and demonstrates a substantial negative magnetoresistance of ~31.5% at 10 K. The magnetoresistance exhibits a butterfly-shaped behaviour at low magnetic fields and becomes almost linear at high magnetic fields. A detailed analysis of the negative magnetoresistance and exchange bias reveals that both phenomena originate from the formation of antiphase boundaries in the as-synthesized NiCo2O4 sample, as confirmed by the high-resolution transmission electron micrograph.
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