Angle-dependent electron spin resonance of YbRh$_2$Si$_2$ measured with planar microwave resonators and in-situ rotation

TL;DR

This study introduces a novel angle-dependent ESR measurement technique for YbRh$_2$Si$_2$ using planar microwave resonators, enabling detailed exploration of its magnetic anisotropy at low temperatures.

Contribution

The paper demonstrates the use of superconducting planar microwave resonators for angle-dependent ESR measurements on YbRh$_2$Si$_2$, providing a new experimental approach for studying magnetic anisotropy.

Findings

ESR g-factor varies with crystallographic angle

Results align with previous high-frequency ESR data

Method shows potential for low-temperature magnetic phase studies

Abstract

We present a new experimental approach to investigate the magnetic properties of the anisotropic heavy-fermion system YbRh$_2$Si$_2$ as a function of crystallographic orientation. Angle-dependent electron spin resonance (ESR) measurements are performed at a low temperature of 1.6 K and at an ESR frequency of 4.4 GHz utilizing a superconducting planar microwave resonator in a $^4$He-cryostat in combination with in-situ sample rotation. The obtained ESR g-factor of YbRh$_2$Si$_2$ as a function of the crystallographic angle is consistent with results of previous measurements using conventional ESR spectrometers at higher frequencies and fields. Perspectives to implement this experimental approach into a dilution refrigerator and to reach the magnetically ordered phase of YbRh$_2$Si$_2$ are discussed.