Imaging magnetic responses of nanomagnets by XPEEM

The Spin resolved Photoelectron Emission Microscope SPEEM is a permanently installed set up at Helmholtz Zentrum Berlin HZB . Due to its specific contrast it is mainly used for magnetic imaging and micro spectroscopy with quantitative analysis. A crucial point in magnetic imaging is the application of magnetic fields. Many experiments require observation of magnetic responses or the preparation of a certain magnetic state during the measurement. We present a dedicated magnetic sample holder combining magnetic field during imaging with additional temperature control. This set up enables SPEEM to measure magnetization curves of individual Fe nanocubes 18 nm 3 in size. If additionally alternating magnetic fields are applied we can image the local magnetic AC susceptibility AC as a function of temperature. The latter is ideally suited to visualize local variations of the Curie temperature TC in nanoand microstructure

Element Specific Magnetic Hysteresis of Individual 18 nm Fe Nanocubes

Correlating the electronic structure and magnetic response with the morphology and crystal structure of the same single ferromagnetic nanoparticle has been up to now an unresolved challenge. Here, we present measurements of the element-specific electronic structure and magnetic response as a function of magnetic field amplitude and orientation for chemically synthesized single Fe nanocubes with 18 nm edge length. Magnetic states and interactions of monomers, dimers, and trimers are analyzed by X-ray photoemission electron microscopy for different particle arrangements. The element-specific electronic structure can be probed and correlated with the changes of magnetic properties. This approach opens new possibilities for a deeper understanding of the collective response of magnetic nanohybrids in multifunctional materials and in nanomagnetic colloidal suspensions used in biomedical and engineering technologies. \ua9 2011 American Chemical Society