Magnetic imaging using nitrogen-vacancy (NV) spins in diamonds is a powerful technique for acquiring quantitative information about sub-micron scale magnetic order. A major challenge for its application in the research on two-dimensional (2D) magnets is the positioning of the NV centers at a well-defined, nanoscale distance to the target material required for detecting the small magnetic fields generated by magnetic monolayers. Here, we develop a diamond “dry-transfer” technique akin to the state-of-the-art 2D-materials assembly methods and use it to place a diamond micro-membrane in direct contact with the 2D interlayer antiferromagnet CrSBr. We harness the resulting NV-sample proximity to spatially resolve the magnetic stray fields generated by the CrSBr, present only where the CrSBr thickness changes by an odd number of layers. From the magnetic stray field of a single uncompensated ferromagnetic layer in the CrSBr, we extract a monolayer magnetization of M_CSB = 0.46(2) T, without the need for exfoliation of monolayer crystals or applying large external magnetic fields. The ability to deterministically place NV-ensemble sensors into contact with target materials and detect ferromagnetic monolayer magnetizations paves the way for quantitative analysis of a wide range of 2D magnets assembled on arbitrary target substrates.

利用钻石中的氮空位 (NV) 自旋进行磁成像是一种获取亚微米级磁序定量信息的强大技术。其在二维 (2D) 磁体研究中应用的一个主要挑战是将 NV 中心定位在距目标材料明确的纳米级距离处，以检测磁性单层产生的小磁场。在这里，我们开发了一种类似于最先进的 2D 材料组装方法的金刚石“干转移”技术，并用它来将金刚石微膜与 2D 层间反铁磁体 CrSBr 直接接触。我们利用所得的 NV 样本接近度来空间解析 CrSBr 产生的杂散磁场，该杂散场仅在 CrSBr 厚度变化奇数层的情况下出现。M _CSB  = 0.46(2) T，无需单层晶体剥离或施加大的外部磁场。确定性地将 NV 整体传感器与目标材料接触并检测铁磁单层磁化强度的能力为对任意目标基板上组装的各种 2D 磁体进行定量分析铺平了道路。