Sharma Vinay, Negusse Ezana, Kumar Ravinder, Budhani Ramesh C
Department of Physics, Morgan State University, Baltimore, Maryland 21251, USA.
Rev Sci Instrum. 2024 Jun 1;95(6). doi: 10.1063/5.0190105.
Ferromagnetic resonance (FMR) spectroscopy is a powerful technique to study the precessional dynamics of magnetization in thin film heterostructures. It provides valuable information about the mechanisms of exchange bias, spin angular momentum transfer across interfaces, and excitation of magnons. A key desirable feature of FMR spectrometers is the capability to study magnetization dynamics over a wide phase space of temperature (T), frequency (f), and magnetic field (B). The design, fabrication, and testing of such a spectrometer, which uses frequency modulation techniques for improved detection of microwave absorption, reduces heat load in the cryostat and allows simultaneous measurements of inverse spin Hall effect (ISHE) induced dc voltages, is described in this paper. The apparatus is based on a 2-port transmitted microwave signal measurement using a grounded co-planar waveguide. The input radio frequency (RF) signal, frequency modulated at a tunable f-band, excites spin precession in the sample, and the attenuated RF signal is measured phase sensitively. The sample stage, inserted in the bore of a superconducting solenoid, allows magnetic field and temperature variability of 0 to ±5 T and 2-310 K, respectively. We demonstrate the working of this Cryo-FMR and ISHE spectrometer on thin films of Ni80Fe20 and Fe60Co20B20 over a wide T, B, and f phase space.
铁磁共振（FMR）光谱学是研究薄膜异质结构中磁化进动动力学的一项强大技术。它提供了关于交换偏置机制、界面处自旋角动量转移以及磁振子激发的有价值信息。FMR光谱仪的一个关键理想特性是能够在温度（T）、频率（f）和磁场（B）的宽相空间内研究磁化动力学。本文描述了这样一种光谱仪的设计、制造和测试，该光谱仪使用频率调制技术来改进微波吸收检测，减少低温恒温器中的热负荷，并允许同时测量逆自旋霍尔效应（ISHE）感应的直流电压。该装置基于使用接地共面波导的双端口传输微波信号测量。输入射频（RF）信号在可调谐f波段进行频率调制，激发样品中的自旋进动，并对衰减的RF信号进行相敏测量。插入超导螺线管孔中的样品台分别允许磁场和温度在0至±5 T和2 - 310 K范围内变化。我们在宽T、B和f相空间内展示了这种低温FMR和ISHE光谱仪在Ni80Fe20和Fe60Co20B20薄膜上的工作情况。
