Magnetic Resonance Force Microscopy Detected Long-Lived Spin Magnetization.
Magnetic Resonance Force Microscopy Detected Long-Lived Spin Magnetization.
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DOI：
10.1109/tmag.2013.2239268
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发表时间：
2013-07
影响因子：
2.1
通讯作者：
Marohn JA
中科院分区：
文献类型：
--
作者：
Chen L;Longenecker JG;Moore EW;Marohn JA
磁共振力显微镜（MRFM）将磁共振成像与扫描探针显微镜相结合，能够对自旋磁化强度进行超灵敏检测。为了在 MRFM 实验中观察动态核极化 (DNP)，这可能会进一步提高其对单质子自旋的灵敏度，制备了掺杂氮氧电子自旋探针的全氘化聚苯乙烯薄膜。将具有 4 μm 直径磁尖的高顺应性悬臂在 7.3 K 的温度和约 0.6 T 的背景磁场中靠近薄膜。用 16.7 GHz 微波照射薄膜，同时实时记录悬臂频率的瞬态变化。除了观察由于硝基氧的电子自旋磁化强度饱和而引起的悬臂频率的预期迅速变化之外，我们还观察到持续的悬臂频率变化。根据其大小、寿命和场依赖性，我们暂时将持续信号归因于通过电子自旋磁化转移产生的极化氘核磁化。通过高磁场梯度中的交叉效应 DNP 机制，进一步测量了持续信号对悬臂振幅和尖端样品分离的依赖性。
Magnetic resonance force microscopy (MRFM), which combines magnetic resonance imaging with scanning probe microscopy together, is capable of performing ultra-sensitive detection of spin magnetization. In an attempt to observe dynamic nuclear polarization (DNP) in an MRFM experiment, which could possibly further improve its sensitivity towards a single proton spin, a film of perdeuterated polystyrene doped with a nitroxide electron-spin probe was prepared. A high-compliance cantilever with a 4 μm diameter magnetic tip was brought near the film at a temperature of 7.3 K and in a background magnetic field of ~0.6 T. The film was irradiated with 16.7 GHz microwaves while the resulting transient change in cantilever frequency was recorded in real time. In addition to observing the expected prompt change in cantilever frequency due to saturation of the nitroxide’s electron-spin magnetization, we observed a persistent cantilever frequency change. Based on its magnitude, lifetime, and field dependence, we tentatively attribute the persistent signal to polarized deuteron magnetization created via transfer of magnetization from electron spins. Further measurements of the persistent signal’s dependence on the cantilever amplitude and tip-sample separation are presented and explained by the cross-effect DNP mechanism in high magnetic field gradients.