# B‑Site Cu2 + Substitution and Strain-Mediated Magnetic Evolution in La2CoRuO6 Double Perovskite: Insights from Experiment and DFT + U‑Corrected Calculations

## TL;DR

This study investigates how substituting Cu2+ for Co2+ in La2CoRuO6 affects its magnetic properties, revealing structural and electronic changes that influence magnetic behavior.

## Contribution

The novel integration of experimental and DFT methods reveals strain- and substitution-driven magnetic evolution in La2CoRuO6.

## Key findings

- Low-level Cu2+ substitution induces a structural transformation from monoclinic to tetragonal phase.
- Strain and mixed valence states lead to competing ferromagnetic and antiferromagnetic interactions.
- Magnetic measurements show a shift in Néel and Curie temperatures with Cu2+ substitution.

## Abstract

Understanding the magnetic ground states of double perovskites
remains complex due to competing exchange interactions, spin–orbit
coupling, and structural disorder. This study explores the substitution
of Cu2
+ for Co2
+ in La2CoRuO6 (LCRO), integrating experimental and DFT
methods to probe the structural and electronic effects influencing
magnetism. Pristine LCRO exhibits a monoclinic P21/c phase with dominant antiferromagnetic
(AFM) Co2
+–O–Ru4
+ interactions. Low-level Cu2
+ substitution
(x = 0.05 and 0.3) induces a strain-driven transformation
to a tetragonal I4/m phase, introducing
structural inhomogeneity and mixed valence states. These lead to competing
ferromagnetic (FM) interactions (Cu2
+–O–Ru4
+/Cu2
+), while AFM order
partially persists at x = 0.3 due to orbital asymmetry
and strain effects. Magnetic measurements and DFT calculations show
a Néel temperature (T
N) shift from
28.7 to 39.8 K (x = 0.05), and emerging FM behavior
at 19.2 K. At x = 0.3, AFM suppression and a Curie
temperature (T
C) of 36.5 K reveal dominant
FM pathways. Finite-size corrected Curie–Weiss analysis highlights
the role of strain and particle size in modulating magnetic properties
and restoring intrinsic behavior in larger particles.