Layered van der Waals 2D magnetic materials are of great interest in fundamental condensed-matter physics research, as well as for potential applications in spintronics and device physics. We present neutron powder diffraction data using new ultrahigh-pressure techniques to measure the magnetic structure of Mott-insulating 2D honeycomb antiferromagnet ${\mathrm{FePS}}_3$ at pressures up to 183 kbar and temperatures down to 80 K. These data are complemented by high-pressure magnetometry and reverse Monte Carlo modeling of the spin configurations. As pressure is applied, the previously measured ambient-pressure magnetic order switches from an antiferromagnetic to a ferromagnetic interplanar interaction and from 2D-like to 3D-like character. The overall antiferromagnetic structure within the $ab$ planes, ferromagnetic chains antiferromagnetically coupled, is preserved, but the magnetic propagation vector is altered from $\mathbf{k}=(0,1,\frac{1}{2})$ to $\mathbf{k}=(0,1,0)$, a halving of the magnetic unit cell size. At higher pressures, coincident with the second structural transition and the insulator-metal transition in this compound, we observe a suppression of this long-range order and emergence of a form of magnetic short-range order which survives above room temperature. Reverse Monte Carlo fitting suggests this phase to be a short-ranged version of the original ambient-pressure structure—with the Fe moment size remaining of similar magnitude and with a return to antiferromagnetic interplanar correlations. The persistence of magnetism well into the HP-II metallic state is an observation in contradiction with previous x-ray spectroscopy results which suggest a spin-crossover transition.

中文翻译：

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调压范德华反铁磁体FePS3中的新兴磁相

分层范德华2D磁性材料在基础凝聚态物理研究以及自旋电子学和器件物理的潜在应用中引起了极大兴趣。我们使用新的超高压技术提供中子粉末衍射数据，以测量Mott绝缘二维蜂窝反铁磁体的磁结构${\mathrm{FePS}}_3$在高达183 kbar的压力和高达80 K的温度下，这些数据得到了高压磁力测定法和自旋构型的反向蒙特卡洛建模的补充。当施加压力时，先前测量的环境压力磁阶从反铁磁相互作用转换为铁磁平面相互作用，并从2D类转换为3D类。内部的整体反铁磁结构$\mathrm{一个}b$ 平面，反铁磁耦合的铁磁链被保留，但是磁传播矢量从 $\mathbf{ķ}=（0，\mathrm{1个}，\frac{\mathrm{1个}}{2}）$ 至 $\mathbf{ķ}=（0，\mathrm{1个}，0）$，磁性单位晶胞尺寸减半。在较高的压力下，与该化合物中的第二个结构转变和绝缘体-金属转变相一致，我们观察到这种长程有抑制作用，并且出现了一种短程有序的磁性形式，这种形式在室温下仍然存在。反向蒙特卡洛拟合表明，该相是原始环境压力结构的短距离版本-Fe矩尺寸保持相似的大小，并且恢复到反铁磁面内相关性。与先前的X射线光谱结果相反，该磁场一直很好地保留到HP-II金属状态，这表明自旋交叉转变。