Transition 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 TC of 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.