Magnetism and Correlated Electrons in LaCr$_2$Ge$_2$N

TL;DR

This study synthesizes and characterizes LaCr$_2$Ge$_2$N, revealing enhanced electron correlations, magnetic ordering phenomena, and electronic structure insights, highlighting the impact of electron count variation in this structural family.

Contribution

It provides the first detailed physical and electronic characterization of LaCr$_2$Ge$_2$N, demonstrating how electron count influences magnetic and electronic properties in this family.

Findings

Enhanced electron correlations with large Sommerfeld coefficient

Magnetic ordering at 14 K and short-range correlations at 460 K

Nearly-flat Cr-3d bands and predicted striped antiferromagnetic ground state

Abstract

We report the synthesis, structure and physical properties of a new quaternary nitride LaCr$_2$Ge$_2$N. The compound crystallizes in the CeCr$_2$Si$_2$C-type structure (P4/mmm), featuring distinctive Cr$_2$N square sheets within Cr$_2$Ge$_2$N block layers. Physical characterizations reveal enhanced electron correlations evidenced by a Sommerfeld coefficient substantially larger than band calculations and pressure-induced deviation from Fermi-liquid behavior. Magnetic measurements show short-range antiferromagnetic correlations developing around 460 K, followed by long-range magnetic ordering at 14 K. Additionally, subtle anomalies at 378 K suggest possible electronic ordering. First-principles calculations reveal nearly-flat Cr-3d bands near the Fermi level and predict a striped antiferromagnetic ground state. This work demonstrates how electron count variation in the CeCr$_2$Si$_2$C-type structure family leads to magnetic ordering in LaCr$_2$Ge$_2$N, contrasting with the paramagnetic behavior of LnCr$_2$Si$_2$C compounds.