Magnetyczne właściwości nanostruktur i spintronika

1. Magnetyczne właściwości nanostruktur i spintronika Bolesław AUGUSTYNIAK

2. Skala... Examples of structures with reduced dimensionality. M.R. Fitzsimmons et al. / Journal of Magnetism and Magnetic Materials 271 (2004) 103–146

3. Length-scales relevant to different magnetic phenomena are shown in purple. In recent years, a number of nanofabrication techniques (shown in blue) have been developed that are capable of making structures whose physical dimensions compete with fundamental magnetic length-scales. Important, also, is the ability to probe magnetism with nanometer sensitivity. Tools suitable for probing magnetic structures across the thin dimension of a film (Z-structures) are shown in orange; those that are applicable to studies of lateral inhomogeneities are shown in green. Theoretical tools (red)are also available that can predict magnetic properties of nanometer-scale structures. Zjawiska magnetyczne w skali nano... M.R. Fitzsimmons et al. / Journal of Magnetism and Magnetic Materials 271 (2004) 103–146

4. X-Ray magnetyczne pomiary Bird’s eye view of the soft X-ray microscope beamline 6.1.2 (XM-1) located at the Advanced Light Source in Berkley, CA. The X-rays enter from the left through the concrete wall into the microscope. Surface Science 601 (2007) 4680–4685; Exploring nanomagnetism with soft X-ray microscopy

5. X-Ray magnetyczne pomiary 2 Schematics of the X-ray optical layout of XM-1 Surface Science 601 (2007) 4680–4685; Exploring nanomagnetism with soft X-ray microscopy

6. Wykorzystanie X-ray dichroizmu X-ray magnetic circular dichroism (X-MCD) detects the difference in the magnetic photoabsorption cross section which depends on the relative orientation between the projection of the specimen’s magnetization onto the photon propagation direction and the helicity of the transmitting X-rays. Strong X-MCD effects up to tens of percent occur in the vicinity of element-specific L3 and L2 absorption edges of transition metals, e.g. Fe, Co, Ni, which correspond to the binding energies of inner core atomic levels, such as the 2p3/2 and 2p1/2 levels, respectively. Surface Science 601 (2007) 4680–4685; Exploring nanomagnetism with soft X-ray microscopy

7. Wykorzystanie X-ray dichroizmu X-ray magnetic circular dichroism (X-MCD) detects the difference in the magnetic photoabsorption cross section which depends on the relative orientation between the projection of the specimen’s magnetization onto the photon propagation direction and the helicity of the transmitting X-rays. Strong X-MCD effects up to tens of percent occur in the vicinity of element-specific L3 and L2 absorption edges of transition metals, e.g. Fe, Co, Ni, which correspond to the binding energies of inner core atomic levels, such as the 2p3/2 and 2p1/2 levels, respectively. Surface Science 601 (2007) 4680–4685; Exploring nanomagnetism with soft X-ray microscopy

8. Przykład b a • Magnetic X-ray image of the domain structure in a CoCrPt nanocrystalline thin film imaged at the Co L3 absorption edge (777 eV)with 15 nm MZP. • Intensity scan across the white bar in the X-ray image (above), indicating a spatial resolution of <15 nm Surface Science 601 (2007) 4680–4685; Exploring nanomagnetism with soft X-ray microscopy

9. Strobowanie Surface Science 601 (2007) 4680–4685; Exploring nanomagnetism with soft X-ray microscopy

10. Magnesowanie...granulek (Top) Hysteresis loop of a nanogranular (Co83Cr17)87Pt13 alloy thin film derived from an integration of the grayscale intensity in magnetic X-ray images taken at the Co L3 absorption edge. The total observation area corresponds to ~2.1 x 1.6 μm2 (300 x 240 pixels). (Center) Field-dependent magnetic domain patterns at various magnetic fields (indicated by the arrows) during the field cycle. A 75 x 75 pixel region is denoted and divided into a 5 x 5 grid pattern used for the determination of local hysteresis loops. Each grid has 15 x 15 pixels (equivalent to 100 x 100 nm2). Materials Today Volume: 9, Issue: 1-2,, 2006, pp. 26-33

11. Motivation Aim: Electron spin + electronics = spintronics Devices: Spin valves, magnetic tunnel transistors, MRAMs, … Outline Model systems: Planar tunnel junctions Recent results: • Fe/MgO/Fe: Influence of the interface structure • Co/vacuum/Co: Zero-bias anomaly

12. Giant Magneto Resistance Fig. 4. (a) Schematic illustration of a longitudinal recording system with a read and write head flying above the recording medium.It is the medium thickness, W is the width of the recorded track, B is the bit size, and d the height the head flies above the medium. (b) Plan-view electron microscope image of a CoPtCrB magnetic alloy longitudinal recording layer. The amorphous grain boundaries are seen as white and the average grain size is 8.5 nm. Shown in the inset is a magnification of a transition region showing the interplay of the medium magnetic properties with the microstructure where D is the media grain size and the transition parameter a approximates the width of the magnetization reversal region. GMR + odczyt informacji G. Srajer et al. / Journal of Magnetism and Magnetic Materials 307 (2006) 1–31

13. Pamięci...

14. Pamięci magnetyczne A storage density of more than 200 Gigabits per square inch has been achieved in demos. Typical storage media consist of a combination of several metals, which segregate into magnetic particles embedded into a non-magnetic matrix that keeps them magnetically independent. A rectangle containing about a hundred particles makes up a bit. Their magnetic orientation is color coded in the figure below. When such a bit is imaged by a magnetic force microscope (on the right) the collection of these particles shows up as white or dark line, depending on the magnetic orientation.

15. MRAM... Magnetoresistive Random Access Memory MRAM is a memory (RAM) technology that uses electron spin to store information (based on Spintronics). MRAM has been called "the ideal memory", potentially combining the density of DRAM with the speed of SRAM and non-volatility of FLASH memory or hard disk, and all this while consuming a very low amount of power. MRAM can resist high radiation, and can operate in extreme temperature conditions, very suited for military and space applications.

16. Time-dependent micromagnetic simulation with random thermal fluctuations of a 4nm NiFeCo MRAM bit patterned as a 0.61.2 mm2 ellipse. The current pulse was given a 2 ns rise time, and the element reversed within 2 ns. Zapis informacji...MRAM G. Srajer et al. / Journal of Magnetism and Magnetic Materials 307 (2006) 1–31

17. (a) Illustration of the spin angular momentum transfer process, (b) A nanostructured thin film pillar structure with a possible spatial distribution of the horizontal-direction magnetization at atime-sliced during reversal is shown using an extended Landau–Lifshitz–Gilbert equation-based finite element numerical simulation, (c) A concentrated charge current injection through a confined area can cause magnetic excitation and spin-wave emission, MRAM... spiny G. Srajer et al. / Journal of Magnetism and Magnetic Materials 307 (2006) 1–31

18. F1 and F2 are the ferromagnetic injector and detector, respectively, represented in their density of state schematics as half-metallic ferromagnets. N is the normal metal that separates them by the edgeto-edge distance L. A schematic density of states of the N-metallic spacer is shown with equal spin-up and spin-down sub-bands filled up to the Fermi level. In the presence of an electrical current, spin-polarized electrons are injected into N from F1. Przełączniki spinowe - koncepcja Conceptual schematic of the lateral spin valve of interest .... S.D. Bader et al. / Superlattices and Microstructures 41 (2007) 72–80

19. Przełączniki spinowe Schematic illustration of a spin valve device employing carbon nanotubes. Non-magnetic layer consists of an oriented carbon nanotube (CNT) array. G. Srajer et al. / Journal of Magnetism and Magnetic Materials 307 (2006) 1–31

20. Przełączniki spinowe ... 2 Magnetoresistance —defined as DR/R (H = 1 T) versus magnetic field for FeCo/Carbon Nanotube array/(Fe nanoparticle) spin valve device at 4.5 K. The negative magnetoresistance is obtained for a sample for which the FeCo layer was allowed to oxidize under ambient conditions for several weeks to form an oxide. The formation of an oxide at the interface between FeCo layer (as a result of aging and thermal treatment) and the CNTarray is the likely origin of the reversal of sign of the spin valve effect. Note the length of the CNTs between the Fe nanoparticle and the FeCo layer is 7 mm.. G. Srajer et al. / Journal of Magnetism and Magnetic Materials 307 (2006) 1–31

21. Molekularny magnetyzm...1 Schematic depiction of the magnetic clusters in Mn12-acetate. Based on Ref. [101], courtesy of M. Sarachik. Single molecule magnets (SMM), which are a class of materials that exhibit a broad range of both conventional and new physical phenomena. SMM are distinct from inorganicbased nanoparticles by virtue of their constituent organic ligands that allow complete localization of the magnetic moments in the ferromagnetic atomic component. Molecular magnets contain a very large number (Avogadro’s) of magnetic molecules that are nominally identical, providing ideal laboratories for the study of nanoscale magnetic phenomena. Possible use: for high-density information storage, as well as the possibility that some members of this materials familycould provide the qubits needed for quantum computation G. Srajer et al. / Journal of Magnetism and Magnetic Materials 307 (2006) 1–31

22. Molekularny magnetyzm...2 Double well potential of Mn12-acetate weakly interacting clusters with doubly-degenerate ground states in zero field. Magnetic relaxation proceeds in these systems by spin reversal via thermal excitation over the anisotropy barrier and/or by quantum tunneling across the potential barrier. Based on Ref. [101], courtesy of M. Sarachik G. Srajer et al. / Journal of Magnetism and Magnetic Materials 307 (2006) 1–31

23. The spinstructure of FeMn in a Co/FeMn thin film heterostructure reorients from the bulk 3Q structure into a quasi-1Q structure in the thin film with preferential moment directions perpendicular to the ferromagnetic Co moments. Upper panel:measurements of d-FeMn. Mossbauer spectroscopy indicates that the 1Q state is not present, while first principles calculations show that the 2Q and 3Q states are the only stable states. The latter is energetically the most favorable. Modelowanie nanostruktur magnetycznych Middle panel: starting spins configuration for a first principles calculation of a FeMn/Co multilayer. Co (green) is assumed to be in a ferromagnetic state while FeMn is initiated in a perfect 3Q state. Lower panel: final configuration after full relaxation of the magnetic state. Co atoms are still perfectly ferromagnetically ordered G. Srajer et al. / Journal of Magnetism and Magnetic Materials 307 (2006) 1–31

24. Magnetyzm metali przejściowych 1 Coexisting Nd crystalline environments in Nd2Fe14B permanent magnet (left). Site-specific Nd hysteresis loops (right). The crystalline environment at the Nd(1) site results in its higher stability against demagnetizing fields. G. Srajer et al. / Journal of Magnetism and Magnetic Materials 307 (2006) 1–31

25. Nanokompozyt z ‘twardej’ i ‘miękkiej’ fazy magnetycznej Left: Schematic of exchange-coupled nanocomposite with hard and soft magnetic phases. Magnetic contributions from Fe atoms in either phase can be separated by selecting appropriate Bragg diffraction conditions (right) and using circularly polarized X-rays at Fe resonance to couple to their magnetic moments. G. Srajer et al. / Journal of Magnetism and Magnetic Materials 307 (2006) 1–31

26. Kompozyty warstwowe Structure of the naturally bilayered manganite, La22xSr1+2x Mn2O7. The MnO6 octahedra denoted in blue and (La,Sr) sites shown as yellow and red dots. The bilayer repeat distance is 10A ˚ . The nonferromagnetic surface bilayer is colored brown G. Srajer et al. / Journal of Magnetism and Magnetic Materials 307 (2006) 1–31

27. Magnetyczne cyrkultory Schematic illustrations of magnetic vortices: (a) simulated magnetization distribution for a circular wafer, (b) atrilayer stack of circular wafers for two ferromagnets sandwiching a non-ferromagnetic spacer, (c) a trilayer ring structure that emphasizes the possibility of spin frustration, and (d) equilibrium magnetization distribution for an elliptical wafer that contains two vortices of opposite chirality. S.D. Bader et al. / Superlattices and Microstructures 41 (2007) 72–80

28. Fotoelektronika z wykorzystaniem światła synchrotronowego 1 Schematic view of an experimental configuration permitting the selective excitation of photoelectrons or fluorescent X-rays from a multilayer magnetic system. Scanning the X-ray spot along the wedge permits scanning the standing wave through the Fe/Cr interface. G. Srajer et al. / Journal of Magnetism and Magnetic Materials 307 (2006) 1–31

29. Magnetyczne bakterie Magnetotactic bacteria. (a) Sketch of typical biotope. (b) Internal compass (up) and its realization (down) by ordered magnetic nanocrystals attached to cytoskeleton strand.

30. Magnetyczne bakterie 2 Magnetotactic bacteria. (a) Sketch of typical biotope. (b) Internal compass (up) and its realization (down) by ordered magnetic nanocrystals attached to cytoskeleton strand. On the northern hemisphere, the local magnetic field is somewhat inclined towards the surface of the earth, pointing downwards. As shown in Fig. 1(a), the direction’north’ is therefore equivalent to ‘down’, whereas ‘south’ is equivalent to ‘up’. Bacteria in search for less oxygen will have to swim down against the oxygen gradient, and thus in a northern direction.The corresponding internal compass for a magnetotactic bacteria living on the northern hemisphere is indicated in Fig. 1(b). The compass needle of the bacteria is called magnetosome. It consists of a chain of likely oriented, and rather tiny magnetic crystals, which are attached to a cellular filament, as shown in Fig. 1(b). According to [14], the basic crystalline materials vary among different groups of magnetotactic bacteria, but the most frequent materials in use seem to be magnetite (Fe3O4) and greigite (Fe3S4). Commun Nonlinear Sci Numer Simulat 15 (2010) 1575–1582

31. TEM images of T7 bacteriophage. (a) normal viruses, (b) ghost virus particles after osmotic shock, (c) ‘‘magnetic viruses’’ with iron oxide nanoparticles at their center; Nanomagnetyzm w medycynie G. Srajer et al. / Journal of Magnetism and Magnetic Materials 307 (2006) 1–31

32. Nanomagnetyzm w medycynie 2 Schematic of fabrication of a magnetic virus. S.D. Bader et al. / Superlattices and Microstructures 41 (2007) 72–80

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