The transition metal thiophosphates MPS_{3} (M=Mn, Fe, Ni) are a class of van der Waals stacked insulating antiferromagnets that can be exfoliated down to the ultrathin limit. MnPS_{3} is particularly interesting because its Néel ordered state breaks both spatial-inversion and time-reversal symmetries, allowing for a linear magnetoelectric phase that is rare among van der Waals materials. However, it is unknown whether this unique magnetic structure of bulk MnPS_{3} remains stable in the ultrathin limit. Using optical second harmonic generation rotational anisotropy, we show that long-range linear magnetoelectric type Néel order in MnPS_{3} persists down to at least 5.3 nm thickness. However an unusual mirror symmetry breaking develops in ultrathin samples on SiO_{2} substrates that is absent in bulk materials, which is likely related to substrate induced strain.

中文翻译：

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光学二次谐波探测超薄MnPS_ {3}中的线性磁电相。

过渡金属硫代磷酸盐MPS_ {3}（M = Mn，Fe，Ni）是一类范德华堆积的绝缘反铁磁体，可以剥落至极薄的极限。MnPS_ {3}特别有趣，因为它的Néel有序状态打破了空间反转和时间反转对称性，从而允许了线性磁电相，这在范德华材料中是罕见的。然而，未知的是，体MnPS_ {3}的这种独特的磁性结构在超薄极限内是否保持稳定。使用光学二次谐波产生旋转各向异性，我们表明MnPS_ {3}中的远程线性磁电类型Néel阶至少可以保持到5.3 nm的厚度。但是，在散装材料中不存在的SiO_ {2}基板上的超薄样品中出现了异常的镜面对称破坏，