8 research outputs found
Effects of lattice geometry on the dynamic properties of dipolar-coupled magnetic nanodisk arrays
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Enhanced magnetic signal along edges of embedded epitaxial La0.7Sr0.3MnO3 nanostructures
When thin films are patterned to realize nanoscale device geometries, maintaining their structural integrity is key to the quality of their functional properties. The introduction of new surfaces and interfaces by lateral modifications may alter material properties as well as the expected device functionality. In this study, two different techniques for nanoscale patterning of epitaxial thin films of La0.7Sr0.3MnO3 are used to investigate the effects on their ferromagnetic properties and film crystalline structure. Nanomagnets are realized as free-standing structures and embedded ferromagnets in a paramagnetic matrix, respectively. We find that the magnetic dichroism signal in x-ray spectomicroscopy is stronger along the edges of the embedded magnets close to TC. X-ray-diffraction measurements reveal a reduction of their in-plane lattice parameters. We discuss how in-plane stress from the nanomagnet surroundings can affect the magnetic properties in these structures
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Effects of array shape and disk ellipticity in dipolar-coupled magnetic metamaterials
Two-dimensional lattices of dipolar-coupled thin film ferromagnetic nanodisks give rise to emergent superferromagnetic (SFM) order when the spacing between dots becomes sufficiently small. In this paper, we define micron-sized arrays of permalloy nanodisks arranged on a hexagonal lattice. The arrays were shaped as hexagons, squares, and rectangles to investigate finite-size effects in the SFM domain structure for such arrays. The resulting domain patterns were examined using x-ray magnetic circular dichroism photoemission electron microscopy. At room temperature, we find these SFM metamaterials to be below their blocking temperature. Distinct differences were found in the magnetic switching characteristics of horizontally and vertically oriented rectangular arrays. The results are corroborated by micromagnetic simulations
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Shape-imposed anisotropy in antiferromagnetic complex oxide nanostructures
In this study, we report on a shape-imposed magnetic anisotropy in micro- and nanostructures defined in antiferromagnetic (AF) LaFeO3 (LFO) thin films. Two distinct types of structures are investigated: embedded magnets created via ion implantation and free-standing magnets created via ion milling. Using a combination of x-ray photoemission electron microscopy and x-ray absorption spectroscopy, we examine the impact of the structure type, AF layer thickness, and crystal geometry on the Néel vector orientation in these structures. We demonstrate a distinct shape-imposed anisotropy in embedded and free-standing structures alike and show that both parallel and perpendicular alignments of the AF spin axis with respect to structure edges can be achieved by variation of the AF layer thickness and the orientation of the structure edges with respect to the LFO crystalline axes. This work demonstrates how the fabrication procedure affects the magnetic order in thin film AF nanostructures and shows how nanoscale patterning can be used to control the orientation of the Néel vector in epitaxial oxide thin films
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Enhanced magnetic signal along edges of embedded epitaxial La0.7Sr0.3MnO3 nanostructures
When thin films are patterned to realize nanoscale device geometries, maintaining their structural integrity is key to the quality of their functional properties. The introduction of new surfaces and interfaces by lateral modifications may alter material properties as well as the expected device functionality. In this study, two different techniques for nanoscale patterning of epitaxial thin films of La0.7Sr0.3MnO3 are used to investigate the effects on their ferromagnetic properties and film crystalline structure. Nanomagnets are realized as free-standing structures and embedded ferromagnets in a paramagnetic matrix, respectively. We find that the magnetic dichroism signal in x-ray spectomicroscopy is stronger along the edges of the embedded magnets close to TC. X-ray-diffraction measurements reveal a reduction of their in-plane lattice parameters. We discuss how in-plane stress from the nanomagnet surroundings can affect the magnetic properties in these structures