Dielectric spectroscopy and magnetoelectric coupling in dilute Fe substituted quasi-one-dimensional spin chain calcium cobalt manganite films

Abstract

Multiferroicity in the type II multiferroic spin chain Ca3CoMnO6 (CCMO) thin films critically depends upon Co/Mn ratio. We intended to disturb this ratio to find its implications on its physical properties. Polycrystalline thin films of pure and dilute Fe substituted CCMO were grown on Pt/Ti/SiO2/Si (100) substrates by pulsed laser deposition. Single rhombohedral phase with R-3c space group for all the samples having a smooth surface with RMS roughness ∼20 nm showed systematic bandgap decrease from 1.75 to 1.38 eV upon Fe substitutions. Enhanced negative magnetoresistance due to magnetostriction has been observed for pure CCMO and dilute Fe doped samples. Magnetodielectric coupling due to both magnetoresistance and magnetostriction origin has been detected, resulting in positive as well as negative values. Dielectric spectroscopy with and without magnetic fields revealed high real permittivity values for pure CCMO and dilute Fe doped CCMO thin films. It is further suggested that dilute Fe substitution (or Mn deficiency) breaks the interchain interactions to some extent, in otherwise the quasi-collinear magnetic chain structure. The surface chemistry and valance states have been analyzed in depth by using x-ray photoelectron spectroscopy.