Short-range magnetic behavior in manganites La0.93K0.07Mn1- x Cu x O3 (0.0 ⩽ x ⩽ 0.09) above the Curie temperature

Abstract

Manganites La_0.93K_0.07Mn_1−x Cu _x O₃ ( 0.0 ⩽ x ⩽ 0.09 ) , prepared by the solid state reaction method at high temperature, were studied structurally and magnetically. The unit cell parameters, as well as bond length d ( Mn,Cu)-O   Å and the bond angle θ ( Mn,Cu)- O 1 -Mn , were determined from the Rietveld refinement of the x-ray diffraction patterns. The Fourier-transform infrared spectroscopy analysis shows that Cu²⁺ substitution induces variations in the vibration modes of the MnO₆ octahedra. Magnetization vs. temperature M T at low magnetic field H=0 .01T were performed in the range <?CDATA $5 < T < 300{{\,K}}$?> 5 < T < 300 K under field coolingand zero field cooling conditions. All the samples exhibited a second-order paramagnetic–ferromagnetic (FM) transition at Curie temperature, T C , in the range between 199 and 285 K. The inverse susceptibility, χ − 1 ( T ) exhibits a linear Curie-Weiss (C-W) behavior for T_{{\text{CW}}}^{\text{*}}$?> ...