Interface-driven ferromagnetism within the quantum wells of a rare earth titanate superlattice

TL;DR

This study uses polarized neutron reflectometry to show that ferromagnetism from a GdTiO$_3$ Mott insulator propagates into adjacent SrTiO$_3$ quantum wells, with well thickness influencing magnetic properties and quantum critical behavior.

Contribution

It reveals how ferromagnetism extends into SrTiO$_3$ quantum wells within a superlattice, highlighting the role of well thickness and interfacial effects in magnetic state stabilization.

Findings

Ferromagnetism propagates into SrTiO$_3$ wells from GdTiO$_3$ matrix.

Well thickness over 5 SrO layers suppresses magnetic moments.

Magnetic states are stabilized by exchange fields and carrier densities.

Abstract

Here we present polarized neutron reflectometry measurements exploring thin film heterostructures comprised of a strongly correlated Mott state, GdTiO$_3$, embedded with SrTiO$_3$ quantum wells. Our results reveal that the net ferromagnetism inherent to the Mott GdTiO$_3$ matrix propagates into the nominally nonmagnetic SrTiO$_3$ quantum wells and tracks the magnetic order parameter of the host Mott insulating matrix. Beyond a well thickness of 5 SrO layers, the magnetic moment within the wells is dramatically suppressed, suggesting that quenched well magnetism comprises the likely origin of quantum critical magnetotransport in this thin film architecture. Our data demonstrate that the interplay between proximate exchange fields and polarity induced carrier densities can stabilize extended magnetic states within SrTiO$_3$ quantum wells.