High temperature magnetic insulating phase in ultrathin La0.67Sr0.33MnO3 films

TL;DR

This study reveals a high-temperature magnetic insulating phase in ultrathin La0.67Sr0.33MnO3 films below 10 unit cells, with potential applications in spintronic tunneling devices.

Contribution

It demonstrates the emergence of a magnetic insulating phase at room temperature in ultrathin films due to structural and magnetic changes.

Findings

Critical thickness for conductivity loss is 10 unit cells.

Curie temperature exceeds 560 K in ultrathin films.

Structural phase transition correlates with magnetic insulating behavior.

Abstract

We present a study of the thickness dependence of magnetism and electrical conductivity in ultra thin La0.67Sr0.33MnO3 films grown on SrTiO3 (110) substrates. We found a critical thickness of 10 unit cells below which the conductivity of the films disappeared and simultaneously the Curie temperature (TC) increased, indicating a magnetic insulating phase at room temperature. These samples have a TC of about 560 K with a significant saturation magnetization of 1.2 +- 0.2 muB/Mn. The canted antiferromagnetic insulating phase in ultra thin films of n< 10 coincides with the occurrence of a higher symmetry structural phase with a different oxygen octahedra rotation pattern. Such a strain engineered phase is an interesting candidate for an insulating tunneling barrier in room temperature spin polarized tunneling devices.