Quddusi H M, Ramsey C M, Gonzalez-Pons J C, Henderson J J, del Barco E, de Loubens G, Kent A D
Physics Department, University of Central Florida, Orlando, Florida 32816-2385, USA.
Rev Sci Instrum. 2008 Jul;79(7):074703. doi: 10.1063/1.2957616.
A sensor that integrates high-sensitivity micro-Hall effect magnetometry and high-frequency electron paramagnetic resonance spectroscopy capabilities on a single semiconductor chip is presented. The Hall-effect magnetometer (HEM) was fabricated from a two-dimensional electron gas GaAsAlGaAs heterostructure in the form of a cross, with a 50 x 50 microm2 sensing area. A high-frequency microstrip resonator is coupled with two small gaps to a transmission line with a 50 Omega impedance. Different resonator lengths are used to obtain quasi-TEM fundamental resonant modes in the frequency range 10-30 GHz. The resonator is positioned on top of the active area of the HEM, where the magnetic field of the fundamental mode is largest, thus optimizing the conversion of microwave power into magnetic field at the sample position. The two gaps coupling the resonator and transmission lines are engineered differently--the gap to the microwave source is designed to optimize the loaded quality factor of the resonator (Q<or=150) while the gap for the transmitted signal is larger. This latter gap minimizes losses and prevents distortion of the resonance while enabling measurement of the transmitted signal. The large filling factor of the resonator permits sensitivities comparable to that of high-quality factor resonant cavities. The integrated sensor enables measurement of the magnetization response of micron scale samples upon application of microwave fields. In particular, the combined measurement of the magnetization change and the microwave power under cw microwave irradiation of single crystal of molecular magnets is used to determine of the energy relaxation time of the molecular spin states. In addition, real-time measurements of the magnetization dynamics upon application of fast microwave pulses are demonstrated.
本文介绍了一种集成在单个半导体芯片上的传感器,它兼具高灵敏度微霍尔效应磁力测量和高频电子顺磁共振光谱功能。霍尔效应磁力计(HEM)由二维电子气GaAs/AlGaAs异质结构制成十字形,传感面积为50×50平方微米。一个高频微带谐振器通过两个小间隙与一个50Ω阻抗的传输线耦合。使用不同的谐振器长度在10 - 30GHz频率范围内获得准TEM基模谐振模式。谐振器位于HEM有源区上方,此处基模磁场最大,从而优化了样品位置处微波功率到磁场的转换。耦合谐振器和传输线的两个间隙设计不同——与微波源相连的间隙旨在优化谐振器的负载品质因数(Q≤150),而传输信号的间隙更大。后一个间隙可使损耗最小化并防止谐振失真,同时能够测量传输信号。谐振器的大填充因数使得灵敏度可与高品质因数谐振腔相媲美。该集成传感器能够测量微米级样品在施加微波场时的磁化响应。特别地,利用分子磁体单晶在连续波微波辐照下磁化变化和微波功率的联合测量来确定分子自旋态的能量弛豫时间。此外,还展示了施加快速微波脉冲时磁化动力学的实时测量。