A magnetostructural phase transition is investigated in single-crystal chromium nitride (CrN) thin films grown by rf plasma molecular beam epitaxy on MgO(001) substrates. While still within the vacuum environment following molecular beam epitaxy growth, in situ low-temperature scanning tunneling microscopy, and in situ variable low-temperature reflection high-energy electron diffraction are applied, revealing an atomically smooth and metallic CrN(001) surface, and an in-plane structural transition from $1\times 1$ (primitive CrN unit cell) to $\sqrt{2}\times \sqrt{2}-R{45}^{\circ }$ with a transition temperature of ($278\pm 3$) K, respectively. Ex situ temperature-dependent measurements using neutron diffraction are also performed, looking at the structural peaks and likewise revealing a first-order structural transition along the [111] out-of-plane direction, with transition temperatures of (268 $\pm$ 3) K. Turning to the magnetic peaks, neutron diffraction confirms a clear magnetic transition from paramagnetic at room temperature to antiferromagnetic at low temperatures with a sharp, first-order phase transition and a Néel temperature of ($270\pm 2$) K or ($280\pm 2$) K for two different films. In addition to the experimental measurements of structural and magnetic ordering, we also discuss results from first-principles theoretical calculations which explore various possible magnetostructural models.

中文翻译：

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射频氮等离子体分子束外延生长氮化铬薄膜的结构和磁性相变

研究了通过射频等离子体分子束外延在MgO（001）衬底上生长的单晶氮化铬（CrN）薄膜的磁结构相变。在分子束外延生长之后仍处于真空环境中的同时，应用了原位低温扫描隧道显微镜和原位可变的低温反射高能电子衍射，揭示了原子上光滑且金属化的CrN（001）表面，以及一个平面内从结构转变$\mathrm{1个}\times \mathrm{1个}$ （原始CrN晶胞） $\sqrt{\mathrm{2个}}\times \sqrt{\mathrm{2个}}-\mathrm{[R}{45}^{\circ }$ 转变温度为（$278\pm 3$）分别。还进行了使用中子衍射的异位温度相关测量，观察了结构峰，并同样揭示了沿[111]面外方向的一阶结构转变，转变温度为（268） $\pm$ 3）K.关于磁峰，中子衍射确认了从室温顺磁性到低温下反铁磁性的清晰磁跃变，具有陡峭的一阶相变且奈埃尔温度为（$270\pm \mathrm{2个}$）K或（$280\pm \mathrm{2个}$）K代表两部不同的电影。除了对结构和磁有序的实验测量之外，我们还讨论了从第一性原理理论计算得出的结果，这些理论探讨了各种可能的磁结构模型。