Tuning spin one channel to exotic orbital two-channel Kondo effect in ferrimagnetic composites of LaNiO3 and CoFe2O4

TL;DR

This study demonstrates the transition from spin one-channel to orbital two-channel Kondo effect in LaNiO3-CoFe2O4 composites by varying CFO content, revealing new insights into electron scattering mechanisms at interfaces.

Contribution

It introduces the tuning of Kondo effects from spin to orbital channels through compositional control in ferrimagnetic composites, highlighting the role of structural interfaces.

Findings

Resistivity upturn appears in composites but not in pure LaNiO3.

Orbital 2CK effect emerges at higher CFO content (15%) with robustness against magnetic fields.

Negative magnetoresistance observed and modeled using spin-dependent scattering analysis.

Abstract

We report the tuning from spin one channel (1CK) to orbital two-channel Kondo (2CK) effect by varying CoFe2O4 (CFO) content in the composites with LaNiO3 (LNO) along with the presence of ferrimagnetism. Although there is no signature of resistivity upturn in case of pure LNO, all the composites exhibit a distinct upturn in the temperature range 30-80 K. For composite with lower percentage of CFO (10 %), the electron spin plays the key role in the emergence of resistivity upturn which is affected by external magnetic field. On the other hand, when the CFO content is increased (15%), the upturn shows strong robustness against high magnetic field (14 T) and a crossover in temperature variation from lnT to T^1/2 at the Kondo temperature, indicating the appearance of orbital 2CK effect. The orbital 2CK effect is originated due to the scattering of conduction electrons from the structural two-level systems which is created at the interfaces between the two phases (LNO and CFO) of different crystal structures as well as inside the crystal planes. A negative magnetoresistance (MR) is observed at low temperature (< 30 K) for composites containing both lower (10 %) and higher percentage (15 %) of CFO. We have analyzed the negative MR using Khosla and Fisher semi-empirical model based on spin dependent scattering of conduction electrons from localized spins.