Enhanced Coercivity in BiFeO3/SrRuO3 heterostructures

Abstract

ABSTRACTTransition metal oxide thin film heterostructures have garnered increasing research interest in the last decade due to their multifunctional properties, such as ferromagnetism and ferroelectricity, which may be utilized in next generation device applications. Many previous works reported on the deposition of such structures on oxide substrates such as SrTiO3, which are not compatible with CMOS applications where Si(100) is the mainstay substrate material. BiFeO3(BFO) is a room temperature insulating ferroelectric and antiferromagnet, a well-known multiferroic material. SrRuO3(SRO) is a ferromagnetic metal with the Curie temperature (TC) of 165K. Unexpected properties emerge when these two dissimilar materials are conjoined. However, there has been no report on exploring the magnetic properties of BFO when it is in contact with SRO, and particularly when they are integrated with Si(100) substrates, which is the subject of present study. BFO/SRO thin films have been epitaxially grown on Si (100) substrates by introducing MgO/TiN epitaxial buffer layers using pulsed laser deposition. BFO thin films show room temperature ferroelectricity as observed from piezo force microscopy (PFM) measurements. The magnetic data collected from BFO thin films show typical antiferromagnetic features as expected. The TCof SRO in all the samples studied was found be ∼ 170K, close to the reported value of 165K. Interestingly, we have noticed that the coercive field of SRO layer increased from 4 kOe to 15 kOe (nearly fourfold) by reducing its thickness from 180 to 23nm, while keeping the thickness of BFO layer constant at 100nm. Pinning of Ru ions by ferroelectric domain walls in BFO, strong interfacial exchange coupling and SRO layer thickness could cause the observed enhancement in coercivity. Our near future work will address the precise underlying mechanisms in greater detail.