Anomalous Hall Effect of Calcium-doped Lanthanum Cobaltite Films

TL;DR

This study investigates the anomalous Hall effect in calcium-doped lanthanum cobaltite films, revealing complex magnetic and transport behaviors linked to spin states and orbital disorder at low temperatures.

Contribution

It provides new insights into the low-temperature Hall effect mechanisms in doped cobaltite films, emphasizing the role of spin-polarized carriers and orbital disorder.

Findings

Large, field-independent Hall resistivity below 100 K

Sign change in Hall resistivity at coercive field

Reentrant metal-insulator transition in x=1/3 film

Abstract

The Hall resistivity, magnetoresistance, and magnetization of La_{1-x}Ca_{x}CoO_{3} epitaxial films with x between 0.25 and 0.4 grown on lanthanum aluminate were measured in fields up to 7 T. The x=1/3 film, shows a reentrant metal insulator transition. Below 100 K, the x=1/3 and 0.4 films have significant coercivity which increases with decreasing temperature. At low temperature the Hall resistivity remains large and essentially field independent in these films, except for a sign change at the coercive field that is more abrupt than the switching of the magnetization. A unique magnetoresistance behavior accompanies this effect. These results are discussed in terms of a percolation picture and the mixed spin state model for this system. We propose that the low-temperature Hall effect is caused by spin-polarized carriers scattering off of orbital disorder in the spin-ordered clusters.