Far-infrared and dc magnetotransport of CaMnO3-CaRuO3superlattices

Abstract

We report temperature and magnetic field dependent measurements of the dc resistivity and the far-infrared reflectivity (photon energies ω = 50 − 700 cm −1 ) of superlattices comprising 10 consecutive unit cells of the antiferromagnetic insulator CaMnO3, and 4 -10 unit cells of the correlated paramagnetic metal CaRuO3. Below the Néel temperature of CaMnO3, the dc resistivity exhibits a logarithmic divergence upon cooling, which is associated with a large negative, isotropic magnetoresistance. The ω → 0 extrapolation of the resistivity extracted from the FIR reflectivity, on the other hand, shows a much weaker temperature and field dependence. We attribute this behavior to scattering of itinerant charge carriers in CaRuO3 from sparse, spatially isolated magnetic defects at the CaMnO3-CaRuO3 interfaces. This field-tunable "transport bottleneck" effect may prove useful for functional metal-oxide devices.

Colloquium: Emergent properties in plane view: Strong correlations at oxide interfaces

“…Theoretical studies substantiate this argument and find that a charge of approximately 0.1 e per interface unit cell leaks across the interface and is confined within ∼1 unit cell at the CaRuO 3 /CaMnO 3 interface (Nanda et al, 2007). Although the magnitude of the charge leakage is small, it has a significant impact on the antiferromagnetic order in the CaMnO 3 , providing a mechanism for spin canting which yields large ferromagnetic moments at the interface Takahashi et al, 2001;Yordanov et al, 2011). To validate this concept a study of the spatial distribution of the magnetism was carried out using X-ray resonant magnetic scattering (XRMS) at the Mn L-edge (Freeland et al, 2005;Kavich et al, 2007).…”

“…One approach to manipulating magnetism involves interfacial charge transfer in heterostructures created from an antiferromagnetic insulator and a paramagnetic metal (Freeland et al, 2010;Takahashi et al, 2001;Yordanov et al, 2011). The choice of materials in this case was determined by two key factors: first, creating moments from a material without any propensity to moment formation, i.e., zero moments, is difficult.…”

Magnetic Interactions at the Nanoscale in Trilayer Titanates

“…In correlated d -electron heterointerfaces, besides the density ratio n m /n c , the dimensionality and orbital polarization of the magnetic interactions are all vital components for the formation of a ground state as exemplified by the emergent FM at the manganate-cuprates [21,22]and manganite-ruthenate interfaces [23][24][25][26]. Moreover, it has been revealed that due to the significantly enhanced quantum fluctuations in reduced dimensions, under the scenario of Kondo state destruction [7,27,28] the electron and spin degrees of freedom start playing a major role to tune the heavy-fermion metal into a magnetic metal phase by crossing the quantum critical point.…”

Cation disorder and epitaxial strain modulated Drude–Smith type terahertz conductivity and Hall-carrier switching in Ca1−xCexRuO3thin films

“…In this relation, ρ 0 is known as residual resistivity and A is called Fermiliquid coefficient. The value of α ~ 1.5, corresponds to nonFermiliquid (NFL) behavior and α ~ 2, is regarded as Fermiliquid (FL) system [13,14]. Applying this theory for analyses of resistivity data of figure 4, we observed that α increases with Cecontent from ~1.3 to ~2.0 for x = 0 to x = 0.1, respectively.…”