Nano granular metallic Fe - oxygen deficient TiO$_{2-\delta}$ composite films: A room temperature, highly carrier polarized magnetic semiconductor

TL;DR

This study reports the fabrication of nano granular Fe-TiO$_{2- ext{delta}}$ composite films exhibiting room-temperature ferromagnetism, high carrier polarization, and potential for nano spintronics applications.

Contribution

It introduces a novel Fe-TiO$_{2- ext{delta}}$ composite film with room-temperature ferromagnetism and high spin-polarized carriers, fabricated via pulsed laser ablation deposition.

Findings

Films show ferromagnetic behavior with 3100 Gauss saturation magnetization.

The composite acts as a p-type magnetic semiconductor at 300 K.

Large anomalous Hall effect indicates strongly spin-polarized holes.

Abstract

Nano granular metallic iron (Fe) and titanium dioxide (TiO$_{2-\delta}$) were co-deposited on (100) lanthanum aluminate (LaAlO$_3$) substrates in a low oxygen chamber pressure using a pulsed laser ablation deposition (PLD) technique. The co-deposition of Fe and TiO$_2$ resulted in $\approx$ 10 nm metallic Fe spherical grains suspended within a TiO$_{2-\delta}$ matrix. The films show ferromagnetic behavior with a saturation magnetization of 3100 Gauss at room temperature. Our estimate of the saturation magnetization based on the size and distribution of the Fe spheres agreed well with the measured value. The film composite structure was characterized as p-type magnetic semiconductor at 300 K with a carrier density of the order of $ 10^{22} /{\rm cm^3}$. The hole carriers were excited at the interface between the nano granular Fe and TiO$_{2-\delta}$ matrix similar to holes excited in the metal/n-type semiconductor interface commonly observed in Metal-Oxide-Semiconductor (MOS) devices. From the large anomalous Hall effect directly observed in these films it follows that the holes at the interface were strongly spin polarized. Structure and magneto transport properties suggested that these PLD films have potential nano spintronics applications.