Short-range magnetic behavior in manganites La_0.93K_0.07Mn_{1- x} Cu _x O₃ (0.0 ⩽ x ⩽ 0.09) above the Curie temperature

Abstract

Manganites La0.93K0.07Mn1−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 5 &lt; T &lt; 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 &gt; T CW * , while for <?CDATA ${T_{\text{C}}} < T T C &lt; T &lt; T CW * , it shows a deviation from the linear behavior predicted by the Heisenberg model. The mentioned deviation of χ − 1 T means that a short ferromagnetic state formation is present even for T &gt; T C , which were characterized by the experimental effective magnetic moment, μ eff exp . A null spontaneous magnetization, m S , above T C was evaluated for all samples by using the Kouvel-Fisher method. This work evaluates the short-range FM clusters by means of an extension of the C-W approach to the <?CDATA ${T_{\text{C}}} < T T C &lt; T &lt; T CW * region, i.e., μ eff exp ( T ) = 2.3 C ( T ) μ B . Finally, the critical coefficient values, β and γ , showed that the 3D Heisenberg model fits adequately the x=0 .0 and x = 0.03 samples, while the 3D Ising model fits the x = 0.09 sample.

Investigation of the structural, electrical, and dielectric properties of La0.5Sm0.2Sr0.3Mn1−xCrxO3 for electrical application

“…Perovskite manganites have been the subject of intense research efforts [1][2][3][4][5] due to the potential technological application of the so-called colossal magnetoresistance (CMR) behavior. [6][7][8] In the last two decades, experiments have focused on the effects of the application of an electric eld on doped manganites. These systems are known to exhibit interesting electronic properties which are explained by many mechanisms.…”

Influence of Nonmagnetic Dilution on the Magnetic Properties of La1−xDyxMn1−yZnyO3 Perovskites at High Temperature

“…These clusters have been, in all cases, related to the mentioned random magnetic disorder. [ 10–16 ] Also, it has been observed that in most of the ceramics doped, both at the site as in the Mn site, the inverse magnetic susceptibility in a certain regime above long‐range order, does not follow the Curie Weiss (CW) law, where C and are Curie constant and paramagnetic (PM) CW temperature, respectively. This law is the asymptotic behavior of magnetization at .…”