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

Abstract

We report the tuning from spin one channel to orbital two-channel Kondo (2CK) effect by varying CoFeO (CFO) content in the composites with LaNiO (LNO) along with the presence of ferrimagnetism. Although there is no signature of resistivity upturn in the case of pure LNO, all the composites exhibit a distinct upturn in the temperature range of 30-80 K. For composites 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 [Formula: see text] to T at the Kondo temperature, indicating the appearance of orbital 2CK effect. The orbital 2CK effect originates 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. The specific heat data at low temperature (⩽40 K), deviates from the usual linear temperature variation of the electronic contribution. With higher CFO content it shows more deviation which also indicates the increasing amount of two-level system. 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.

Metal–Insulator Transition of LaNiO3 Films in LaNiO3/SrIrO3 Heterostructures

“…film thickness, associated with a dimensional crossover in conductivity from three dimensions to two dimensions . This low-temperature carrier localization can be ascribed to random scattering of electrons by microstructural disorders and the interference of electron wave functions that traps the electrons and thus increases the resistivity . In the present work, the 10 u.c.…”

Electrical transport properties and Kondo effect in La1−xPrxNiO3−δ thin films

“…This effect lowers the scattering of conduction electrons by localized impurity spins, leading to a decrease in resistivity 52 . Several reports have successfully interpreted the negative MR using this model, in In 1−x Mn x Sb films 53 , amorphous Cr-doped In 2 O 3 films 54 , and (1−x)LNO + xCoFe 2 O 4 (CFO) polycrystalline 55 . The semi-empirical formula of the negative MR 52 given by Khosla and Fisher is expressed by This formula is based on the third-order expansion of the s-d exchange Hamiltonian which yields the logarithmic temperature variation of resistivity.…”

Effect of LaNiO3 on the impedance and dielectric properties of CoFe2O4: a high temperature study

“…The nanoparticles (nps) of LaNiO 3 (LNO) and CoFe 2 O 4 (CFO) have been synthesized by citric acid assisted sol-gel method [8]. The two powders of LNO and CFO are mixed and ground to get a homogeneous mixture and heated at 650 • C. To measure dielectric properties, the heat treated powder is pressed into pellet and sintered at 700 • C.…”

“…In our previous report, we have seen that the defects inside the crystalline planes and at the interfaces between these two crystalline phases influence the charge transport [8]. Therefore we can expect these defects will help to trap more space charges and will effect the impedance and dielectric properties.…”

“…The advantage of tuning the properties by varying compositions have made the composites very popular materials in the field of multiferroics [1,2], superconductivity [3,4] or to improve mechanical and thermal properties [5] or magneto transport properties [6,7]. From our previous studies, we have seen that the structural defects have huge impact on the transport properties of the composites containing LaNiO 3 (LNO) and CoFe 2 O 4 (CFO) [8]. Therefore, it will be interesting to correlate the electrical properties with the microstructure of the composite materials.…”