Cu-doping induced ferromagnetic insulating behavior and domain wall pinning effects in LaMnO3

Abstract

A systematic study on the structural, magnetic, and electrical transport properties was performed for the LaMn 1−x Cu x O 3 system. A single phase of orthorhombic perovskite structure was formed for x = 0.05-0.40. A striking paramagnetic-ferromagnetic transition and a considerable magnetoresistance effect were observed at the ferromagnetic ordering temperature T C , but no insulator-metal transition induced by Cu-doping was observed. Below T C , a visible unexpected drop was observed in the ac susceptibility and zero-field-cooled dc magnetization for the dilute doped samples with x ≤ 0.10, which was proven to be associated with domain wall pinning effects by milling the bulk material into single domain particles. It is validated that there is no exchange interaction between Cu and Mn, and double exchange interactions between Mn 3+ and Mn 4+ are induced by Cu-doping in the anti-ferromagnetic LaMnO 3 matrix, whereas the severe distortion and disorder caused by occupied-dopant prohibits charge carriers from hopping.

Dopants in Lanthanum Manganite: Insights from First-Principles Chemical Space Exploration

“…Among these, the most stable ones (i.e., those that display the darkest green quarters) are those involving the alkali and alkaline earth elements (i.e., K, Rb, Cs, Ca, Sr, Ba). Indeed, all these findings are entirely consistent with available experimental evidence for both La − and Mn , site doping. We note though that K, Rb and Cs have not been considered in experimental work in the past, and hence, constitute new dopants identified by this study.…”

Effect of Metal-Oxide Phase on the Magnetic and Magnetocaloric Properties of La0.7Ca0.3MnO3-MO (MO=CuO, CoO, and NiO) Composite

“…On the other hand, superfluous Cu 2+ resulting from an increase in CuO content in the composite occupied B sites between Mn 3+ and Mn 4+ , and would induce disorder and change the bond angle and bond length of Mn-O-Mn interaction, and, thus, weaken the double-exchange interaction. Accordingly, T C and Ms decreased with the gradual increase in doping level [54,55]. A similar mechanism could be responsible for the observed decrease in magnetization at 5 K in the LCMO-MO composite.…”