Quantification of charge-to-strain mediated interface coupling transfiguration in FE/FSMA multiferroic heterostructures
Thickness modulated direct, local measurement of magnetoelectric (ME) coupling was executed in a high quality sputter deposited PZT/Ni-Mn-In bilayer system grown on Si(1 0 0) substrate. The additive temperature and magnetic-field-driven shape-memory behavior of bottom ferromagnetic (FM) Ni-Mn-In layer, which vanish at ultra-low regime (8 nm), induce fluctuations in the dielectric and ferroelectric (FE) characteristic of PZT. The prominent magnetic-field-modulated P-E loops registered at room temperature in ±400 kV cm-1 electric field range illustrate the presence of giant strain-mediated direct ME coupling in bilayers. This giant strain-mediated direct ME coupling in bilayers can be imputed to magnetic-field-actuated shape-memory behavior of Ni-Mn-In film. The I-V characteristic depicts that the PZT/Ni-Mn-In bilayer endures transition from Ohmic conduction (dominant at low field) to interface-limited Fowler-Nordheim (FN) tunneling prevailing at high electric field. Magnetic measurements of the bilayer revealed that voltage-attuned magnetic anisotropy variation was strongly dependent on the thickness of the bilayer. The normalized magnetization (M/M s) versus electric field (ME) plots was sketched to cognize the origin of interfacial converse ME coupling. The occurrence of butterfly-shaped ME loops showed the dominance of strain-mediated coupling in the (200 nm/220 nm) bilayer, in contrast to (40 nm/8 nm) heterostructure coupling which was purely charge mediated. The co-existence of charge- and strain-mediated ME coupling in (80 nm/30 nm) structure was evident from quite asymmetric features of ME curves. In 80 nm/30 nm multiferroic heterostructure two reversible and stable magnetic field states of Ni-Mn-In were observed at zero electric field. Such a non-volatile switching of magnetization accomplished by reversing the electric field could prove useful in future MERAM devices.