Simultaneous imaging of the ferromagnetic and ferroelectric structure in multiferroic heterostructures

By measuring the spin polarization of secondary electrons and the intensity of backscattered electrons generated in a scanning electron microscope, we are able to simultaneously image the ferromagnetic domain structure of a ferromagnetic thin film and the ferroelectric domain structure of the underlying ferroelectric substrate upon which it is grown. Simultaneous imaging allows straightforward, quantitative measurements of the correlations in these complex multiferroic systems. We have successfully imaged domains in CoFe/BFO and Fe/BTO, two systems with very different ferromagnet/ferroelectric coupling mechanisms, demonstrating how this technique provides a new local probe of magneto electric/strictive effects in multiferroic heterostructures.ISSN:2166-532

Magnetic microscopy and simulation of strain-mediated control of magnetization in PMN-PT/Ni nanostructures

Strain-mediated thin film multiferroics comprising piezoelectric/ferromagnetic heterostructures enable the electrical manipulation of magnetization with much greater efficiency than other methods; however, the investigation of nanostructures fabricated from these materials is limited. Here we characterize ferromagnetic Ni nanostructures grown on a ferroelectric PMN-PT substrate using scanning electron microscopy with polarization analysis (SEMPA) and micromagnetic simulations. The magnetization of the Ni nanostructures can be controlled with a combination of sample geometry and applied electric field, which strains the ferroelectric substrate and changes the magnetization via magnetoelastic coupling. We evaluate two types of simulations of ferromagnetic nanostructures on strained ferroelectric substrates: conventional micromagnetic simulations including a simple uniaxial strain, and coupled micromagnetic-elastodynamic simulations. Both simulations qualitatively capture the response of the magnetization changes produced by the applied strain, with the coupled solution providing more accurate representation

Magnetic microscopy and simulation of strain-mediated control of magnetization in PMN-PT/Ni nanostructures

Strain-mediated thin film multiferroics comprising piezoelectric/ferromagnetic heterostructures enable the electrical manipulation of magnetization with much greater efficiency than other methods; however, the investigation of nanostructures fabricated from these materials is limited. Here we characterize ferromagnetic Ni nanostructures grown on a ferroelectric PMN-PT substrate using scanning electron microscopy with polarization analysis (SEMPA) and micromagnetic simulations. The magnetization of the Ni nanostructures can be controlled with a combination of sample geometry and applied electric field, which strains the ferroelectric substrate and changes the magnetization via magnetoelastic coupling. We evaluate two types of simulations of ferromagnetic nanostructures on strained ferroelectric substrates: conventional micromagnetic simulations including a simple uniaxial strain, and coupled micromagnetic-elastodynamic simulations. Both simulations qualitatively capture the response of the magnetization changes produced by the applied strain, with the coupled solution providing more accurate representation.Comment: 10 pages, 4 figure

Realization of ground-state artificial skyrmion lattices at room temperature.

The topological nature of magnetic skyrmions leads to extraordinary properties that provide new insights into fundamental problems of magnetism and exciting potentials for novel magnetic technologies. Prerequisite are systems exhibiting skyrmion lattices at ambient conditions, which have been elusive so far. Here, we demonstrate the realization of artificial Bloch skyrmion lattices over extended areas in their ground state at room temperature by patterning asymmetric magnetic nanodots with controlled circularity on an underlayer with perpendicular magnetic anisotropy (PMA). Polarity is controlled by a tailored magnetic field sequence and demonstrated in magnetometry measurements. The vortex structure is imprinted from the dots into the interfacial region of the underlayer via suppression of the PMA by a critical ion-irradiation step. The imprinted skyrmion lattices are identified directly with polarized neutron reflectometry and confirmed by magnetoresistance measurements. Our results demonstrate an exciting platform to explore room-temperature ground-state skyrmion lattices

Direct observation of spin configurations and classification of switching processes in mesoscopic ferromagnetic rings

Using nonintrusive imaging techniques we have directly observed the nanoscopic details of the magnetization configurations of epitaxial and polycrystalline mesoscopic ring structures with a <15-nm resolution. We have found head to head domain walls with different spin structures depending on ring width. Further, we can classify the geometry dependent switching processes according to the number of transitions (single, double, triple) that a ring undergoes in a hysteresis cycle. In the case of triple switching we find a state with a complete vortex core present in the ring