Investigation of element-specific and bulk magnetism, electronic and crystal structures of La{0.70}Ca{0.30}Mn{1-x}Cr{x}O{3}

TL;DR

This study explores the magnetic, electronic, and structural properties of La{0.70}Ca{0.30}Mn{1-x}Cr{x}O{3} using advanced spectroscopic and diffraction techniques, revealing complex magnetic behaviors and stable valence states across different compositions.

Contribution

It provides detailed element-specific magnetic and electronic insights into La{0.70}Ca{0.30}Mn{1-x}Cr{x}O{3}, highlighting the interplay of exchange interactions and valence states with composition.

Findings

Stable Cr{3+} ions confirmed by XAS.

Ferrimagnetic state observed at x=0.15 below 224 K.

Antiferromagnetic order at x=0.70 below 258 K.

Abstract

The magnetic interactions in La{0.70}Ca{0.30}Mn{1-x}Cr{x}O{3} (x = 0.15, 0.50 and 0.70) are investigated by x-ray absorption spectroscopy (XAS), x-ray magnetic circular dichroism (XMCD), high-resolution x-ray powder diffraction, and bulk magnetization measurements. XAS in the Mn and Cr L{2,3} edges support stable single valent Cr{3+} ions and a varying Mn valence state with x, while the O K edge XAS spectrum reveals local maxima in the O 2p density of states close to the Fermi level due to mixing with Mn and Cr 3d states. A robust antiferromagnetic state is found for x=0.70 below TN = 258 K. For x=0.15, combined XMCD and bulk magnetization measurements indicate a fully polarized ferrimagnetic state for the Mn and Cr spins below Tc=224 K. For x=0.50, a reduced ferrimagnetic component dominated by Mn spins is present below Tc=154 K. No evidence of lattice anomalies due to cooperative charge and orbital orderings is found by x-ray diffraction for all samples. The magnetic properties of this system are rationalized in terms of a competition of ferromagnetic Mn-Mn double exchange and antiferromagnetic Cr-Cr and Cr-Mn superexchange interactions.