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arXiv 1812.03215cond-mat.supr-con
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一种免冷冻变温扫描SQUID显微镜

Cryogen-free variable temperature scanning SQUID microscope

Logan Bishop-Van Horn, Zheng Cui, John R. Kirtley, Kathryn A. Moler

摘要:

扫描超导量子干涉仪(SQUID)显微镜是一种强大的工具,用于成像材料和设备的局部磁特性,但它需要一个低振动的低温环境,传统上通过与液氦浴或“湿”稀释制冷机的混合室热接触来实现。我们安装SQUID显微镜上的3 K板的Bluefors制冷机和其振动光谱的特点,通过测量SQUID噪声在一个区域的急剧通量梯度。通过实施被动隔振,我们将传感器-样品的相对振动减少到20 nm面内和15 nm面外。与SQUID传感器热隔离的变温样品台可在2.8 K至110 K的样品温度下进行测量。我们证明了这些进展,通过成像不均匀的抗磁化率和涡旋钉扎在最佳掺杂的YBCO高于90 K。

英文摘要:

Scanning Superconducting QUantum Interference Device (SQUID) microscopy is a powerful tool for imaging local magnetic properties of materials and devices, but it requires a low-vibration cryogenic environment, traditionally achieved by thermal contact with a bath of liquid helium or the mixing chamber of a "wet" dilution refrigerator. We mount a SQUID microscope on the 3 K plate of a Bluefors cryocooler and characterize its vibration spectrum by measuring SQUID noise in a region of sharp flux gradient. By implementing passive vibration isolation, we reduce relative sensor-sample vibrations to 20 nm in-plane and 15 nm out-of-plane. A variable-temperature sample stage that is thermally isolated from the SQUID sensor enables measurement at sample temperatures from 2.8 K to 110 K. We demonstrate these advances by imaging inhomogeneous diamagnetic susceptibility and vortex pinning in optimally-doped YBCO above 90 K.

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