Thickness dependent structural, magnetic, and electronic properties of the epitaxial films of transparent conducting oxide NiCo2O4

Abstract

We present the thickness dependent structural, magnetic, and transport properties of transparent conducting spinel NiCo2O4 thin films on MgAl2O4 (001) substrates. The structural examination of the films reveals that the epitaxial stain is independent of the films' thickness. Electric and magnetic measurements show that the films are metallic with p-type conduction and ferrimagnetic down to 2 unit cells with an enhanced coercive field in the films thinner than 30 unit cells. The low-temperature resistivity data indicate that the observed resistivity minimum results from the disorder-induced quantum interference effects. Our results demonstrate that NiCo2O4 may provide an alternative magnetic conducting medium for spintronics devices.

Atomic layer deposition of nickel–cobalt spinel thin films

“…14,19,21,22,[53][54][55] Most often, (Co 2/3 Ni 1/3 ) 3 O 4 is described as ferrimagnetic resulting from superexchange between Ni ions on the O h site and Co ions on the T d site. 54 However, the various ionic species possible in this material result in many different exchange pairs with negative as well as positive interactions.…”

“…Similarly, the magnetic nature of (Co 2/3 Ni 1/3 ) 3 O 4 depends strongly on the deposition method and has been shown to be related to the electrical transport mechanism. 19,21,22 Having the eye on the potential applications of semiconducting oxides, atomic layer deposition (ALD) provides us with a number of advantages over other thin-film fabrication techniques. It can be easily scaled up to commercially relevant dimensions and furthermore allows the coating of difficult morphologies and the fabrication of precisely dimensioned heterostructures such as superlattices.…”

Cationic structure and charge transport in sol–gel-derived nickel-cobaltite thin films

“…Thus, for the films with x C 0.5, the post-annealing temperature was reduced to 500°C for suppressing the formation of NiO phase in the film. There have been reports for fabricating NiCo 2 O 4 films in which the growth temperature is important for evading NiO phase: below 400°C for electrostatic spray deposition [3] and 300-400°C for pulsed-laser deposition [4]. For the Co 3 O 4 film used as a baseline sample, the post-annealing temperature was 800°C.…”

“…Lapham et al [3] employed an electrostatic spray deposition method to obtain films consisting of NiCo 2 O 4 and Co 3 O 4 on alumina substrates. Silwal et al [4] deposited NiCo 2 O 4 thin films with varying thickness (3-700 nm) on MgAl 2 O 4 (001) substrates by a pulsed-laser deposition. They obtained the electrical resistivity as low as 1.4 9 10 -3 X cm for the film with thickness of 180 nm.…”

Origin of metallic behavior in NiCo2O4 ferrimagnet

“…Up to date, most of the investigations have been on polycrystalline materials and the reports on single crystalline NCO are very few42526272829. Epitaxial thin films of spinel NiCo 2 O 4 films grown at lower temperatures (<450 °C) are reported to be ferrimagnetic with metallic characteristics while those grown at higher temperatures are non-magnetic and insulating26.…”