# Investigation of Ionic and Anomalous Magnetic Behavior in CrSe$_2$ Using $^8$Li $\beta$-NMR

## TL;DR

This study uses $^8$Li $eta$-NMR to explore magnetic and ionic behaviors in CrSe$_2$, revealing two distinct environments and ionic diffusion effects across a wide temperature range.

## Contribution

It provides new insights into the magnetic environments and ionic diffusion in CrSe$_2$ using $^8$Li $eta$-NMR, highlighting two magnetically distinct sites and diffusion-related relaxation.

## Key findings

- Identification of two magnetically distinct environments for $^8$Li in CrSe$_2$
- Observation of ionic diffusion onset above 200 K
- Detection of a magnetic transition near 20 K

## Abstract

We have studied a mosaic of 1T-CrSe$_2$ single crystals using $\beta$-detected nuclear magnetic resonance of $^{8}$Li from 4 to 300 K. We identify two broad resonances that show no evidence of quadrupolar splitting, indicating two magnetically distinct environments for the implanted ion. We observe stretched exponential spin lattice relaxation and a corresponding rate ($1/T_1$) that increases monotonically above 200 K, consistent with the onset of ionic diffusion. A pronounced maximum in $1/T_1$ is observed at the low temperature magnetic transition near 20 K. Between these limits, $1/T_1$ instead exhibits a broad minimum with a remarkable absence of strong features in the vicinity of structural and magnetic transitions between 150 and 200 K. Together, the results suggest $^{8}$Li$^{+}$ site occupation within the van der Waals gap between CrSe$_2$ trilayers. Possible origins of the two environments are discussed.