FIRB Microsistemi e Nanomateriali Magnetici Tematica T4 Films e Multistrati Nanocompositi Magnetici Multistrato Laboratorio Superfici M. Carbucicchio, M. Rateo, M. Prezioso, F. Zini Dipartimento di Fisica – Università di Parma Steve Bennett Department of Synchrotron Radiation Daresbury Laboratory Warrington, UK Frank J. Berry Department of Chemistry The Open University Milton Keyness, UK Michel Labrune Laboratoire PMTM-CNRS Université Paris-13 Villetaneuse, France Collaborazioni: G. Asti, M. Ghidini, M. Solzi Laboratorio Magnetometria Dip. Fisica, Università, Parma A. Paoluzi, G. Turilli Laboratorio IMEM CNR, Parma

Ultra-High Vacuum Growth by Electron Beams Vacuum:Starting10 -8 PaOperating Pa Deposition Rate:0.5 ÷ 0.8 nm/min Substrates:Amorphous Quartz Si(100), Si(111) no native oxide removal

Characterization: Auger Electron Spectroscopy Layer Thickness, Very Low Contamination Grazing Incidence X-Ray Diffraction (SRS Daresbury, UK) Crystallographic Structure, Textures, Grain Sizes Grazing Incidence X-Ray Reflection (SRS Daresbury, UK) Thickness, Density, Interface Roughness Atomic Force Microscopy Morphology of Surfaces Transmission Electron Microscopy (Erlangen, DE) Morphology of Multilayers and Interfaces Conversion Electron Mössbauer Spectroscopy Composition and Dimensions of Interfaces Direction of Magnetization Magnetic Force Microscopy Magnetic Domains 1. Model System Co/Fe + Co MultilayersCo:5.0 ÷ 15.0 nm Fe0.5 ÷ 45.0 nm 2. RE-TM Systems Co/NdFeB/Co + Mo Nd 2 Fe 14 B arc evaporated 5[SmCo/Fe] + SmCo + AuSmCo 5 arc evaporated 3[SmCo/Co]SmCo 5 from 10[Sm0.3/Co0.5] Co/SmCo 5 /CoSmCo 5 co-evaporated Materials:

In-plane AGFM Hysteresis Loops (IMEM) Interaction-based deviation parameter M R = saturation remanence I IRM (H) = isothermal remanence I DCD (H) = dc demagnetization remanence M > 0 positive exchange coupling (ferromagnetic interaction) Model System: simple materials soft/hard ratio = 3

Pure Iron Interfaces H hf distribution: - main peak (35 T) narrow linewidth similar sublattices sharp Fe concentration gradient - small peak (32 T) broad linewidth a few Fe into Co Interface Analysis : CEMS

For Fe layer thickness up to 24 nm Strong Uniaxial Magnetic Anisotropy Hard Axis Low Hysteresis (M r /M s 0) Easy Axis High Squareness (M r /M s 1) Remanence ratio M r /M s vs the in-plane applied magnetic field angle 180° periodicity with |sin | behaviour Anisotropy constant K 1 ( ) 10 4 erg/cm 3 Co 5nm /Fe 2nm Magnetic Anisotropy AGFM Hysteresis Loops (IMEM)

Fe layer thickness: < 5 nm in-plane magnetization 5 24 nm out-of-plane ~10° > 24 nm out-of-plane ~40° No stray fields Stretched domains Stripe domains CEMSMFM

First Endeavors: RE-TM Hard Layer AGFM Hysteresis Loop (IMEM) Problems:- Uncoupled Phases - Low Coercive Field - Composition

Single Phase Magnetic Behaviour AGFM Hysteresis Loop (IMEM) Problems:- Stoichiometry - Reproducibility - Interdiffusion (GIXRR, CEMS) CEMS for 5[SmCo/Fe] + SmCo + Au

AGFM Hysteresis Loop (IMEM) Synchrotron Radiation GIXRD Pattern Single Phase Magnetic Behaviour Low Coercive Field: Nanostructuration SmCo 5 Stoichiometry

Future Activities TEM and HEED Analyses both in plane and in cross-section - Morphology, Defectivity - Continuity, Thickness of layers - Grain Sizes, Crystallographic textures - Phase Composition Mapping - Roughness, Interdiffusion, Dimensions of Interfaces Synchrotron Radiation GIXRD - Phase Composition - Grain Size, Textures - Kind and Intensities of Stresses - Depth-profiling: different X-ray incidence angles Ultra-High Vacuum Electron Beam Deposition of - RE-TM Films with High Coercive Fields - RE-TM/Fe Bilayers and Multilayers AFM and MFM observations - Morphology - Magnetic Domains CEMS - Composition and Dimensions of Interfaces - Direction of Magnetization