Toward in operando measurements of nano-scale transport within devices: High-frequency XFMR

We have developed an instrument for performing high-frequency, atomic core level spectroscopy. The instrument uses extreme ultraviolet (EUV) light that is intrinsically synchronized to an RF excitation that can range from 80 MHz to >60 GHz,[1] and can probe with elemental resolution a variety of transport dynamics excited thus. The element-specificity is provided using EUV light (tunable from 10nm – 100nm) generated by high-harmonic generation (HHG). The phase-synchronized microwaves are generated by an RF frequency comb generator with the laser oscillator pulse train as an input. This results in a timing jitter of less than 1.1 ps between the microwave phase and the EUV pulses, thereby supporting resonant studies at 100 GHz or higher.

As a demonstration, we used this instrument to perform high-frequency, x-ray detected ferromagnetic resonance spectroscopy (XFMR) of three magnetic thin-film samples on opaque silicon substrates. XFMR is widely used at synchrotron light sources to study magnetic/spin dynamics at and across interfaces, but has not before been performed at the laboratory scale and is usually limited to frequencies below 12 GHz.[2] The ability to perform XFMR at higher frequencies enables studies of materials with high magnetic anisotropy, in addition to ferrimagnets, antiferromagnets, and high-wavevector excitations in nanodevices. The measurements shown here highlight the ability of our instrument to perform high-frequency, element- and/or layer-resolved XFMR, and can be combined with ptychographic reflectometry for enhanced sensitivity as well as 3D nano-scale resolution.[3]