# Quasi-quartet crystal electric field ground state in a tetragonal CeAg$_2$Ge$_2$ single crystal

## TL;DR

This study reports the growth and characterization of CeAg$_2$Ge$_2$ single crystals, revealing a quasi-quartet ground state and anisotropic magnetic properties, including antiferromagnetism and metamagnetic transitions, through comprehensive physical measurements.

## Contribution

First successful growth of CeAg$_2$Ge$_2$ single crystals and detailed analysis showing a quasi-quartet crystal electric field ground state.

## Key findings

- CeAg$_2$Ge$_2$ exhibits antiferromagnetic order at 4.6 K.
- Strong magnetic anisotropy observed in resistivity and susceptibility.
- Presence of closely spaced energy levels indicating a quasi-quartet ground state.

## Abstract

We have successfully grown the single crystals of CeAg$_2$Ge$_2$, for the first time, by flux method and studied the anisotropic physical properties by measuring the electrical resistivity, magnetic susceptibility and specific heat. We found that CeAg$_2$Ge$_2$ undergoes an antiferromagnetic transition at $T_{\rm N}$ = 4.6 K. The electrical resistivity and susceptibility data reveal strong anisotropic magnetic properties. The magnetization measured at $T$ = 2 K exhibited two metamagnetic transitions at $H_{\rm m1}$ = 31 kOe and $H_{\rm m2}$ = 44.7 kOe, for $H \parallel$ [100] with a saturation magnetization of 1.6 $\mu_{\rm B}$/Ce. The crystalline electric field (CEF) analysis of the inverse susceptibility data reveals that the ground state and the first excited states of CeAg$_2$Ge$_2$ are closely spaced indicating a quasi-quartet ground state. The specific heat data lend further support to the presence of closely spaced energy levels.