Constructing a magnetic handle for antiferromagnetic manganites

Abstract

An intrinsic property of antiferromagnetic materials is the compensation of the magnetic moments from the individual atoms that prohibits the direct interaction of the spin lattice with an external magnetic field. To overcome this limitation we have created artificial spin structures by heteroepitaxy between two bulk antiferromagnets ${\mathrm{SrMnO}}_{3}$ and ${\mathrm{NdMnO}}_{3}$. Here, we demonstrate that charge transfer at the interface results in the creation of thin ferromagnetic layers adjacent to $A$-type antiferromagnetism in thick ${\mathrm{NdMnO}}_{3}$ layers. A novel interference based neutron diffraction technique and polarized neutron reflectometry are used to confirm the presence of ferromagnetism in the ${\mathrm{SrMnO}}_{3}$ layers and to probe the relative alignment of antiferromagnetic spins induced by the coupling at the ferro- to antiferromagnet interface. A density functional theory analysis of the driving forces for the exchange reveals strong ferromagnetic interfacial coupling through quantifiable short range charge transfer. These results confirm a layer-by-layer control of magnetic arrangements that constitutes a promising step on a path towards isothermal magnetic control of antiferromagnetic arrangements as would be necessary in spin-based heterostructures like multiferroic devices.