Room temperature spin polarized magnetic semiconductor

TL;DR

This study demonstrates room temperature ferromagnetism in layered Fe/TiO₂-δ films, revealing their potential as p-type magnetic semiconductors for spintronic applications due to interface hole polarization.

Contribution

It introduces a novel layered Fe/TiO₂-δ structure exhibiting room temperature ferromagnetism and spin polarization at interfaces, advancing magnetic semiconductor research.

Findings

Films show ferromagnetism from 4K to 400K.

Layered structure is p-type magnetic semiconductor at 300K.

Holes at the interface are spin-polarized under magnetic field.

Abstract

Alternating layers of granular Iron (Fe) and Titanium dioxide (TiO$_{2-\delta}$) were deposited on (100) Lanthanum aluminate (LaAlO$_3$) substrates in low oxygen chamber pressure using a controlled pulsed laser ablation deposition technique. The total thickness of the film was about 200 nm. The films show ferromagnetic behavior for temperatures ranging from 4 to $400 ^oK$. The layered film structure was characterized as p-type magnetic semiconductor at $300 ^oK$ with a carrier density of the order of $10^{20} /cm^3$. The undoped pure TiO$_{2-\delta}$ film was characterized as an n-type magnetic semiconductor. The hole carriers were excited at the interface between the granular Fe and TiO$_{2-\delta}$ layers similar to holes excited in the metal/n-type semiconductor interface commonly observed in Metal-Oxide-Semiconductor (MOS) devices. The holes at the interface were polarized in an applied magnetic field raising the possibility that these granular MOS structures can be utilized for practical spintronic device applications.