Champaign-One of the current challenges presented by manganites is the poor spin polarization of ... more Champaign-One of the current challenges presented by manganites is the poor spin polarization of tunnel currents in spintronic devices due to degradation of the magnetic order at interfaces. The systems investigated are perovskite La 1−x Sr x MnO 3 (300Å) with a thin cap layer of STO(8Å) and a similar structure with a modified LaMnO 3 (8Å) /STO(8Å) cap grown by ozoneassisted ALL-MBE. Detailed fitting of x-ray resonant magnetic scattering (XRMS) spectra allows direct characterization and comparison of the interface magnetic profiles. The XRMS indicates a smoothly varying profile of ∼40Å depth with dramatically reduced surface magnetization and a reversible evolution as a function of temperature. Comparison of the magnetic profiles shows that changing the capping layer (equivalent to reducing the interface hole doping) has a negligible effect on the reduced magnetic order.
The technique of spark erosion can be used to prepare magnetlc fine particles of almost any compo... more The technique of spark erosion can be used to prepare magnetlc fine particles of almost any composition in sizes from a few nm to tens of µm. The spark erosion method is described, including several recent improvements designed to permit the production of ultrafine particles without contamination.
Instability of surface magnetism in the manganites is currently an area not well understood. In o... more Instability of surface magnetism in the manganites is currently an area not well understood. In our previous work using exploring loss of ferromagnetic (FM) order at the surfaces of layered manganites, we found clear evidence for an intrinsic insulating non-FM surface layer atop adjacent ferromagnetic subsurface layers.[1] The presence of a non-FM surface layer of one bilayer thickness was observed
Instability of surface magnetism in the manganites is currently an area not well understood. In o... more Instability of surface magnetism in the manganites is currently an area not well understood. In our previous work using exploring loss of ferromagnetic (FM) order at the surfaces of layered manganites, we found clear evidence for an intrinsic insulating non-FM surface layer atop adjacent ferromagnetic subsurface layers.[1] The presence of a non-FM surface layer of one bilayer thickness was observed
Using polarized X-rays, we compare the electronic and magnetic properties of a La 2/3 Sr 1/3 MnO3... more Using polarized X-rays, we compare the electronic and magnetic properties of a La 2/3 Sr 1/3 MnO3(LSMO)/SrTiO3(STO) and a modified LSMO/LaMnO3(LMO)/STO interface. Using the technique of X-ray resonant magnetic scattering (XRMS), we can probe the interfaces of complicated layered structures and quantitatively model depth-dependent magnetic profiles as a function of distance from the interface. Comparisons of the average electronic and magnetic properties at the interface are made independently using X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD). The XAS and the XMCD demonstrate that the electronic and magnetic structure of the LMO layer at the modified interface is qualitatively equivalent to the underlying LSMO film. From the temperature dependence of the XMCD, it is found that the near surface magnetization for both interfaces falls off faster than the bulk. For all temperatures in the range of 50K-300K, the magnetic profiles for both systems always show a ferromagnetic component at the interface with a significantly suppressed magnetization that evolves to the bulk value over a length scale of ∼1.6-2.4 nm. The LSMO/LMO/STO interface shows a larger ferromagnetic (FM) moment than the LSMO/STO interface, however the difference is only substantial at low temperature.
Champaign-One of the current challenges presented by manganites is the poor spin polarization of ... more Champaign-One of the current challenges presented by manganites is the poor spin polarization of tunnel currents in spintronic devices due to degradation of the magnetic order at interfaces. The systems investigated are perovskite La 1−x Sr x MnO 3 (300Å) with a thin cap layer of STO(8Å) and a similar structure with a modified LaMnO 3 (8Å) /STO(8Å) cap grown by ozoneassisted ALL-MBE. Detailed fitting of x-ray resonant magnetic scattering (XRMS) spectra allows direct characterization and comparison of the interface magnetic profiles. The XRMS indicates a smoothly varying profile of ∼40Å depth with dramatically reduced surface magnetization and a reversible evolution as a function of temperature. Comparison of the magnetic profiles shows that changing the capping layer (equivalent to reducing the interface hole doping) has a negligible effect on the reduced magnetic order.
The technique of spark erosion can be used to prepare magnetlc fine particles of almost any compo... more The technique of spark erosion can be used to prepare magnetlc fine particles of almost any composition in sizes from a few nm to tens of µm. The spark erosion method is described, including several recent improvements designed to permit the production of ultrafine particles without contamination.
Instability of surface magnetism in the manganites is currently an area not well understood. In o... more Instability of surface magnetism in the manganites is currently an area not well understood. In our previous work using exploring loss of ferromagnetic (FM) order at the surfaces of layered manganites, we found clear evidence for an intrinsic insulating non-FM surface layer atop adjacent ferromagnetic subsurface layers.[1] The presence of a non-FM surface layer of one bilayer thickness was observed
Instability of surface magnetism in the manganites is currently an area not well understood. In o... more Instability of surface magnetism in the manganites is currently an area not well understood. In our previous work using exploring loss of ferromagnetic (FM) order at the surfaces of layered manganites, we found clear evidence for an intrinsic insulating non-FM surface layer atop adjacent ferromagnetic subsurface layers.[1] The presence of a non-FM surface layer of one bilayer thickness was observed
Using polarized X-rays, we compare the electronic and magnetic properties of a La 2/3 Sr 1/3 MnO3... more Using polarized X-rays, we compare the electronic and magnetic properties of a La 2/3 Sr 1/3 MnO3(LSMO)/SrTiO3(STO) and a modified LSMO/LaMnO3(LMO)/STO interface. Using the technique of X-ray resonant magnetic scattering (XRMS), we can probe the interfaces of complicated layered structures and quantitatively model depth-dependent magnetic profiles as a function of distance from the interface. Comparisons of the average electronic and magnetic properties at the interface are made independently using X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD). The XAS and the XMCD demonstrate that the electronic and magnetic structure of the LMO layer at the modified interface is qualitatively equivalent to the underlying LSMO film. From the temperature dependence of the XMCD, it is found that the near surface magnetization for both interfaces falls off faster than the bulk. For all temperatures in the range of 50K-300K, the magnetic profiles for both systems always show a ferromagnetic component at the interface with a significantly suppressed magnetization that evolves to the bulk value over a length scale of ∼1.6-2.4 nm. The LSMO/LMO/STO interface shows a larger ferromagnetic (FM) moment than the LSMO/STO interface, however the difference is only substantial at low temperature.
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Papers by Richard Kodama