Alexander Granovsky Moscow State University, Moscow 119991, Russia

1. Modern Magnetism: Introduction Toward energy efficiency • Alexander Granovsky • Moscow State University, Moscow 119991, Russia • Ikerbasque Visiting Professor 5th March – the World Energy Efficiency day 25th Jan. – Birthday of Moscow State University

2. 15 institutes 40 Faculties 50.000 students 10.000 staff 2 ships, 6 subdiv. Supercomputer Sputnik 1755

3. Magnetism Department was founded more than 70 years ago. The hysteresis loop was measured in MSU by Prof. Stoletov in 1872. Stoletov, Arkad’ev, Landau, Kapitza, Kondorski • The main topics: • Advanced Magnetic Materials (nanostructures, soft and hard, amorphous and nanocrystalline, thin films, ribbons, microwires, carbon nanotubes, multilayers “ferromagnet/superconductor” etc) • Spintronics • Magnetophotonics (magnetooptics, magnetophotonic crystals) • Room temperature dilute magnetic semiconductors and oxides • Magnetic liquids and polymers • Magnetic sensors • Biomagnetism • 36 departments, • 2500 students • PhD students • 800 staff

4. Outline • Introduction • Magnetic refrigirators • Magnetic Recording • Spintronics • Magnetophotonics • Diluted Magnetic Semiconductors • Magnetism in Biology and Medicine • Conclusions “I swear to tell the truth, all the truth and nothing but the truth”

5. Motivation • “The nation that controls magnetism will control the universe” • Dick Tracy - 1935 Dick Tracy by Dick Locher and Michael Killian All materials are magnetic!!!

6. Magnetic Materials: World Market Distribution Soft 8.8 billion Euros Semihard 15.5 billion Euros Hard 7.3 billion Euros

7. 1 wind turbine- 250 kg NdFeB

8. Magnetic sensors • Operating at room temperature • High sensitivity (10-8 Oe for medicine) • High spatial resolution (1-10 nm for magnetic heads) • Low dimensions • Low cost ($ 0.3 for autocar industry) Magnetic Sensors are used for speed, rotational speed, linear position, linear angle and position measurement in automotive, industrial and consumer applications. Toyota uses 86 types of magnetic sensors

11. Magnetocaloric effect 15% 50% USA

14. МАГНИТНЫЕ ХОЛОДИЛЬНЫЕ МАШИНЫ

15. МАГНИТНЫЕ ХОЛОДИЛЬНЫЕ МАШИНЫ

17. Saving 30% of energy Ecologically-friendly Gd is the best material We are working to find novel materials

19. Magnetic Information Storage • Density: 20 Gb/in2 • Speed: 200 Mb/s • Size: f2.5” x 2 • Capacity: 50 Gb • Density: 2 kb/in2 • Speed: 70 kb/s • Size: f24” x 50 • Capacity: 5 Mb 2010 100 Gb/in2

20. 20 Gb/in2 Near the Superparamagnetic Limit !! Magnetic Recording Working Group on Magnetism and Magnetic Materials Chair: David Awschalom, University of California, Santa Barbara Facilitators: Joachim Stöhr, IBM Almaden Research Center, and Jeffrey Kortright, Lawrence Berkeley National Laboratory http://www-als.lbl.gov/als/workshops/scidirecthtml/4Magnetic/magnetic.html Computer disks consist of granular magnetic materials like CoPtCr with admixtures of boron or tantalum in order to minimize the transition width between the magnetic domains. In the disk material, the grains are believed to be coated by a non magnetic shell that reduces the magnetic coupling between the grains. A small transition width is required in order to achieve a high magnetic-flux density in the direction perpendicular to the disk surface, as shown. The flux from the spinning disk is sensed by the spin-valve magnetic read head. [Figure: J. Stöhr, IBM Research Center.]

21. Present and Future of Hard-Disks IBM has demonstrated a GMR head with an areal density capability greater than 35.3 billion bits per square inch, and laboratory demonstrations beyond 50 Gbits/in2 have been reported, indicating that future disk drives could exhibit capacities at least two times higher than today. Disk drives will continue to be enhanced through the use of MEMS micro-actuators, fluid bearing spindle motors and even split or multiple actuators. Also, new data storage techniques, as holographic storage are on horizon. http://www.storage.ibm.com/technolo/grochows/g19.htm

22. Attacking Superparamagnetism Modifying magnetic properties of the media is a front up approach to delaying superparamagnetism, and increasing Ku the energy barrier to magnetic reversal per grain volume is an effective means of accomplishing this. New magnetic materials and films are being investigated and applied to further delay the superparamagnetic phenomenon resulting in good media stability. http://www.storage.ibm.com/technolo/grochows/g17.htm

24. Tunnel microscope manipulation 1 byte =8 bit=96 atoms Nowaday -108 atoms 12 atoms of Fe – artificial antiferomagnet The smallest magnetic memory cell

25. Electronics, Micro- and Nanoelectronics Charge of Electron SPINTRONICS= SPIN+TRANSPORT+ELECTRONICS (1992) Spintronics Charge + Spin of Electron Spin control and manipulation Spin current without dissipation!!!!? Quantum Computers

28. Future: From charge current to pure spin current Spin Hall Effect

29. I. Newton 1727 1643

30. Introduction Yes, I discovered Faraday effect! 1845 1845 Michael Faraday (1791-1867)

32. Electronics, Micro- and Nanoelectronics Charge of Electron Spintronics Charge + Spin of Electron • Magnetophotonics = Spintronics at microwave, infrared and optical frequencies Charge+Spin of Electron+ Photon • Manipulating light with a magnetic field • Manipulating charge and magnetization with a light • Photons do not couple directly to magnetic field or magnetization, but its interaction with magnetic materials depends on • Charge of electrons • Spin of electrons • Photon frequency • Interaction between charge and spin MAGNETOOPTICAL EFFECTS ARE EXTREMELY WEAK !!!

33. Linear Magneto-optics • Surface sensitive (10-30 nm for metals) • MO micromagnetometer (0.5 mkm spatial resolution, 4-400K) • Vector-MOKE • Domain Observation and Magnetization Reversal • MO spectroscopy – (composition, structure, electronic band structure) • Determination of spin polarization • Ultrafast Spin Dynamics and Domain Wall Motion (1 femtosec) • Cheap Nonlinear Magneto-optics • One-layer sensitive • Interfaces and Structural Transformation • Expensive

35. How to increase the interaction between photons and magnetic materials to develop tunable by a week magnetic field optical and high frequency devices? Resonances Multiple interference New effects

36. Photonic Crystals Artificial optical material with optical-wavelength scale structures One-dimensional Two-dimensional Three-dimensional Dielectric e1 Dielectric e1 Dielectric e1 Dielectric e2 Dielectric e2 Dielectric e2 Traditional multilayer film Prepared by a film formation technique such as sputtering method

37. Introduction Bi:YIG (thickness dM) SiO2 Observed Ta2O5 1 0 0 ] % Theory [ 8 0 T e c 720 [nm] 720 [nm] 720 [nm] n 6 0 63 [%] 63 [%] 63 [%] a t t i m (SiO2/Ta2O5)k (Ta2O5/SiO2)k 4 0 s n Magnetization a r 2 0 T 0 ] . 0 g e d [ F q 10times Bi:YIG single-layer film n o i t 720 [nm] 720 [nm] 720 [nm] - 0 . 5 a t o -0.63 [deg.] -0.63 [deg.] -0.63 [deg.] r y a d a r a F - 1 5 0 0 6 0 0 7 0 0 8 0 0 9 0 0 l W a v e l e n g t h [ n m ] MAGNETOPHOTONIC CRYSTALS M. Inoue, 1997 Review on MPC: M. Inoue, A.Granovsky et al J. Phys. D 2006, Springer v.94, 2007 MOSLIM !!!!

38. Introduction Cd1-хMnxSe, Hg1-xMnxTe Low Temperature before1987 AIIBVI:Mn Furdyna Zavadskii Nagaev Ohno Dietl Matsumoto Coey Dubroca Kaminski& Sarma DMS GaAs:Mn (Tc=173 K) Room Temperature Si:Mn (>400K) 2004 2001 TiO2-:Co (600-800 K) DMO ZnO:TM, SnO2:TM, CeO2:TM etc, TM=Mn, Co, Fe 2004 Si , HfO2 magnetism=quasiferromagnetism d0 TiO2, ZnO, In2O3, Nanoparticles CeO2, Al2O3, ZnO, In2O3. et al. FM in nanostructures 2006 There is an ongoing quest for ferromagnetic semiconductorswith a Curie temperature well above room temperature,which could be used for a second generation of spin electronics, as well as a search for transparent ferromagnetswhich can add an optoelectronic dimension.

39. Intrinsic Ferromagnetism High Curie Temperature High spin-polarization Semiconducting properties Transparent for light Homogeneity • Questions: • Intrinsic or Extrinsic? (parasitic phases and ferromagnetic clusters) • Which ions bear magnetic moment? • Type of exchange? (carrier-mediated, superexchange, percolation etc) • Does a TM doping play key role? Si:Mn and TiO2-:Co

40. Magnetism in Medicine and Biology Magnetic therapy for healing has been around for centuries. Many ancient civilizations, such as the Greeks, Hebrews, Indians, Chinese and Egyptians, used magnets for medical purposes. It's only been recently that using magnets has come back into medical use. No one exactly knows how the magnets promote healing, but it's theorized that magnets attract metal elements in the body, such as iron in blood, to increase blood circulation and therefore instigate healing. Knowledge in this field is comparatively poor, even in the case of physicists. Although hemoglobin, the blood protein that carries oxygen, is weakly diamagneticand is repulsed by magnetic fields, the magnets used in magnetic therapy are many orders of magnitude too weak to have any measurable effect on blood flow.

41. Pain Relief The increase in blood flow from magnets delivers more oxygen and natural painkillers called endorphins, which in turn relieves minor pain. Anti-Inflammatory In addition to relieving pain, magnets can reduce inflammation with the increased blood circulation. When inflammation decreases, the body can also heal more quickly. Detoxification Magnets can also attract the positive charges of various toxins created by the body's immune system when fighting infection. The increased blood flow will then escort the toxins to the liver for speedy detoxification and eventual elimination from the body through the kidneys. Multiple Sclerosis Several case studies have found that magnetic fields seem to relieve symptoms of MS. Treatment with pulsed electromagnetic fields seems to relieve pain and muscle spasms as well as improve fatigue, cognition, vision and bladder control. Magnetic Resonance Imaging Magnetic Resonance Imaging (MRI) is one of the more popular forms of radiology, which uses a magnetic field scanner to detect the positively charged ions of water throughout the human body. The resulting radiographs display stark contrasts between the various soft tissues throughout the body, which has made it the preferred radiology technique for neurological and musculoskeletal imaging.

42. The magnetic therapy business is so large that over 120 million people all around the world are using some type of magnetic therapy product. Magnets can be worn in many different styles. The most popular styles are forms of jewelry, like bracelets, watches, necklaces, anklets, and rings.

43. Magneticseparation, drug delivery, hyperthermia treatments andmagnetic resonance imaging (MRI) contrast enhancement. Tagging is made possible through chemical modification of the surface of the magnetic nanoparticles, usually bycoating with biocompatible molecules such as dextran, polyvinylalcohol (PVA ) and phosopholipids—all of which have beenused on iron oxide nanoparticles

44. Drug Delivery The objectives are two-fold: (i) to reduce the amount ofsystemic distribution of the cytotoxic drug, thus reducingthe associated side-effects; and (ii) to reduce the dosagerequired by more efficient, localized targeting of thedrug. In magnetically targeted therapy, a cytotoxic drug isattached to a biocompatible magnetic nanoparticle carrier.These drug/carrier complexes—usually in the form of abiocompatible ferrofluid—are injected into the patient viathe circulatory system. When the particles have entered thebloodstream, external, high-gradient magnetic fields are usedto concentrate the complex at a specific target site within thebody

45. Magnetocardiography (MCG) is a technique to measure the magnetic fields produced by electrical activity in the heart using extremely sensitive devices such as the Superconducting Quantum Interference Device (SQUID). If the magnetic field is measured using a multichannel device, a map of the magnetic field is obtained over the chest; from such a map, using mathematical algorithms that take into account the conductivity structure of the torso, it is possible to locate the source of the activity. For example, sources of abnormal rhythms or arrhythmia, may be located using MCG. Magnetoencephalography (MEG) is a technique for mapping brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain, using arrays of SQUIDs. Applications of MEG include basic research into perceptual and cognitive brain processes, localizing regions affected by pathology before surgical removal, determining the function of various parts of the brain, and neurofeedback

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