Incoherent Effect of Fe and Ni Substitutions in the Ferromagnetic-Insulator La0.6Bi0.4MnO3+d

TL;DR

This study compares how Fe and Ni doping affect the magnetic and electronic properties of La0.6Bi0.4MnO3, revealing opposite shifts in ferromagnetic transition temperatures and differences in magnetic hardness and resistivity.

Contribution

It provides new insights into how Fe and Ni substitutions differently influence magnetic ordering, transition temperatures, and electronic behavior in bismuth-based manganite perovskites.

Findings

Ni doping increases TC to ~200 K

Fe doping decreases TC to ~95 K

Ni-doped material shows soft ferromagnetism

Abstract

A comparative study of the effect of Fe and Ni doping on the bismuth based perovskite La0.6Bi0.4MnO3.1, a projected spintronics magnetic semiconductor has been carried out. The doped systems show an expressive change in magnetic ordering temperature. However, the shifts in ferromagnetic transition (TC) of these doped phases are in opposite direction with respect to the parent phase TC of 115 K. The Ni-doped phase shows an increase in TC ~200 K, whereas the Fe-doped phase exhibits a downward shift to TC~95 K. Moreover, the Fe-doped is hard-type whereas the Ni-doped compound is soft-type ferromagnet. It is observed that the materials are semiconducting in the ferromagnetic phase with activation energies of 77 & 82 meV for Fe & Ni-doped phases respectively. In the presence of external magnetic field of 7 Tesla, they exhibit minor changes in the resistivity behaviours and the maximum isothermal magnetoresistance is around -20 % at 125 K for the Ni-phase. The results are explained on the basis of electronic phase separation and competing ferromagnetic and antiferromagnetic interactions between the various mixed valence cations.