2，2-二苯基-1-苦肼基（DPPH）分子L带电子顺磁共振的磁阻抗检测
Magnetoimpedance based detection of L-band electron paramagnetic resonance in 2,2-diphenyl-1-picrylhydrazyl (DPPH) molecule
摘要：
使用在固定频率（9和10 GHz之间）谐振的微波腔检测电子顺磁共振（EPR）仍然是迄今为止最流行的方法。在这里，我们报告了一种无腔技术，它只使用一个阻抗分析仪和一个铜带线圈检测L波段EPR（f = 1-3 GHz）在标准EPR标记2，2-二苯基-1-苦基肼（DPPH）。我们的方法依赖于测量磁阻抗（MI）响应DPPH通过一个铜带线圈，包围DPPH。与仅测量功率吸收的场导数的商业EPR相比，我们的方法使我们能够推导出吸收和色散。在线圈中的射频电流的不同频率（f = 0.9至2.5 GHz）下，测量了在扫描外部直流磁场时铜带的电阻（R）和电抗（X）的变化。R在直流磁场的临界值处表现出尖锐的峰值，这被识别为谐振场，并且X在相同频率处表现出色散。分析数据以获得线宽和谐振场参数。共振场随频率线性增加，在X波段测得的Landég因子为1.999，接近于可接受值2.0036。该技术的简单性可用于研究催化和其他材料中的顺磁中心。
英文摘要：
Detection of electron paramagnetic resonance (EPR) using a microwave cavity resonating at a fixed frequency (between 9 and 10 GHz) remains the most popular method until now. Here, we report a cavity-less technique which makes use of only an impedance analyzer and a copper strip coil to detect L-band EPR (f = 1-3 GHz) in the standard EPR marker 2,2-diphenyl-1-picrylhydrazyl (DPPH). Our method relies on measuring the magnetoimpedance (MI) response of DPPH through a copper strip coil that encloses DPPH. In contrast to commercial EPR which measures only the field derivative of power absorption, our method enables us to deduce both absorption and dispersion. Changes in resistance (R) and reactance (X) of the copper strip while sweeping an external dc magnetic field, were measured for different frequencies (f = 0.9 to 2.5 GHz) of radio-frequency current in the coil. R exhibits a sharp peak at a critical value of the dc magnetic field, which is identified as the resonance field and X shows a dispersion at the same frequency. The data were analyzed to obtain line width and resonance field parameters. The resonance field increased linearly with frequency and the obtained Landé g factor of 1.999 is close to the accepted value of 2.0036, measured in X-band. The simplicity of this technique can be exploited to study paramagnetic centers in catalysis and other materials.
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