AI 中文总结
通过磁化和热容测量，发现结构有序的NiS$_2$纳米晶保持体材料的两步反铁磁转变，并在低温下表现出矫顽力、交换偏置和垂直回线位移的滞后铁磁响应，归因于纳米晶表面未补偿磁矩。
AI 中文摘要
结构有序的NiS$_2$纳米晶，平均直径为$27.0 \pm 6.5$ nm，通过磁化和热容测量显示，保持了类似体材料的两步反铁磁转变。在较低转变温度以下，纳米晶表现出具有大矫顽力、交换偏置和场冷后垂直回线位移的滞后铁磁响应，而刚好在转变温度以上的$M$-$H$响应几乎是线性的。这些特征最好地解释为低温反铁磁序在纳米晶表面终止时产生的未补偿表面磁矩。没有明显的额外体材料弱铁磁组分限制了均匀倾斜模型，并间接支持了体材料NiS$_2$弱铁磁性的畴壁场景。
英文摘要
Structurally well-ordered NiS$_2$ nanocrystals with an average diameter of $27.0 \pm 6.5$ nm retain the bulk-like two-step antiferromagnetic transitions, as shown by magnetization and heat-capacity measurements. Below the lower transition, the nanocrystals exhibit a hysteretic ferromagnetic response with large coercivity, exchange bias, and a vertical loop shift after field cooling, whereas the $M$-$H$ response just above the transition is nearly linear. These features are best explained by uncompensated surface moments generated where the low-temperature antiferromagnetic order terminates at the nanocrystal surface. The absence of a clear additional bulk-like weak-ferromagnetic component constrains homogeneous-canting models and indirectly favors a domain-wall scenario for the weak ferromagnetism of bulk NiS$_2$.
Comments5 pages, 4 figures
Journal refJ. Phys. Soc. Jpn. 95 (2026) 103702
