ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΚΑΙ ΥΨΗΛΗ ΤΕΧΝΟΛΟΓΙΑ: Από τη µαγνητική ροπή του ηλεκτρονίου σε εφαρµογές καθηµερινές και µελλοντικές

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1 ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΚΑΙ ΥΨΗΛΗ ΤΕΧΝΟΛΟΓΙΑ: Από τη µαγνητική ροπή του ηλεκτρονίου σε εφαρµογές καθηµερινές και µελλοντικές ρ.. Νιάρχος Iνστιτούτο Επιστήµης Υλικών ΕΚΕΦΕ «ΗΜΟΚΡΙΤΟΣ» ΟΜΗ ΟΜΙΛΙΑΣ Η µαγνητική ροπή του ηλετρονίου και του ατόµου Η µαγνητική ροπή πολλών ατόµων Κατηγορίες µαγνητιkών υλικών Από τους νανοµαγνήτες στους γνωστούς µαγνήτες Εφαρµογές µαγνητικών υλικών - Μαγνητική εγγραφή - Αισθητήρες - Ιατρικές Εφαρµογές Magnetic Hyperthermia - Bιοιατρικές Εφαρµογές - ιαστηµικές εφαρµογές Μαγνητοηλεκτρικά- σπιν τρανζίστορ D-SCHOOL-05 1

2 VARIOUS SCALES Å mm m µm nm D-SCHOOL-05 2

3 Discovering Magnetism Supposedly, about 4,000 years ago in Minor Asia a shepard named Magnes discovered magnetism when the nails in his shoes stuck to a rock. This was because of the iron deposits in the rock. He called the rock magnetite, but it was never decided if he named it after himself or after the town he came from, Magnesia. By A.D. 1200, Chinese and European sailors used magnetic compasses to steer their ships. D-SCHOOL-05 3

4 Gilbert s Discovery William Gilbert published a book called "De Magnete" which became the standard one in Europe for electrical and magnetic phenomena. Magnus magnes ipse est globus terrestris. [The whole Earth is a magnet.] William Gilbert D-SCHOOL-05 4

5 A Magnetic Perpetual Motion Machine The US patent office was issuing patents for magnetic perpetual motion machines as late as the 1970's. D-SCHOOL-05 5

6 Scale of Magnet Field 650 T The Strongest Destructive Pulsed Magnet 0.4 T lodestone/magnetite (Fe 3 O 4 ) 60 T long pulse magnet 33 T continuous field magnet 0.3T house refrigerator magnets 3*10-5 T Surface of earth 2 T MRI machine 0.4 T stereo speaker magnets 3*10-10 T produced by human body 1 Tesla = 10 4 Oe D-SCHOOL-05 6

7 Uses of Magnetism Motors used in Cars, Airplanes and everywhere Magnetic Cranes Computer HardDrive MRI Magnetic levitation Train Etc. etc D-SCHOOL-05 7

8 ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΚΑΙ ΥΨΗΛΗ ΤΕΧΝΟΛΟΓΙΑ: Από τη µαγνητική ροπή του ηλεκτρονίου σε εφαρµογές καθηµερινές και µελλοντικές VARIOUS MAGNETIC FIELDS D-SCHOOL-05 8

9 ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΚΑΙ ΥΨΗΛΗ ΤΕΧΝΟΛΟΓΙΑ: Από τη µαγνητική ροπή του ηλεκτρονίου σε εφαρµογές καθηµερινές και µελλοντικές The Bohr Atom Electrons Nucleus Orbit / Energy Level Atomic Structure to X-Rays 16 Atomic Atomic Spectra Spectra and and Bohr Bohr Model Model Atomic Atomic Spectra Spectra and and Bohr Bohr Model Model (2) (2) One One view view of of atomic atomic structure structure in in early early 20th 20th Bohr Bohr said said classical classical view view is is wrong. wrong. century century was was that that an an electron electron (e-) (e-) traveled traveled Need Need a a new new theory theory now now called called QUANTUM QUANTUM about about the the nucleus nucleus in in an an orbit. orbit. or or WAVE WAVE MECHANICS. MECHANICS. Electron Electron e- e- can can only only exist exist in in certain certain discrete discrete orbits orbits orbit + orbit called called stationary stationary states. states Classically Classically any any orbit orbit should should be be possible possible and and so so is is any any energy. e- e- is is restricted restricted to to QUANTIZED QUANTIZED energy energy states. states. energy But But a a charged charged particle particle moving moving in in an an Energy Energy of of state state = --C/n C/n 2 electric electric field field should should emit emit energy. 2 where where energy. C C is is a a CONSTANT CONSTANT End End result result should should be be destruction! n destruction! n = = QUANTUM QUANTUM NUMBER, NUMBER, n n = = 1, 1, 2, 2, 3, 3, 4, 4, D-SCHOOL-05 9

10 THE ELECTRON and ITS PROPERTIES Discovery of the Electron Cathode Rays Red Hot Energy Transfer -ve cathode +ve anode In 1897 J.J. Thompson proposed the rather startling hypothesis that cathode rays were streams of negatively charged particles electrons. Atomic Structure to X-Rays 3 D-SCHOOL-05 10

11 ORIGIN OF MAGNETIC MOMENTς Magnetic moment originates from the motion of electrons SPIN ROTATION: S D-SCHOOL-05 11

12 ORIGIN OF MAGNETISM IN ATOMS Dipole Moments in Atoms Lecture 22-2 Electron as Source of Magnetism in Atoms In the classical picture of atoms, the electrons orbit the nuclei, and they also spin on their axes. Both of these effects produce current loops, and these current loops in turn produce magnetic dipole moments. Orbital angular momentum of an electron v 2 e q ur µ l = ( e) πr = ( rmev) = L 2π r 2m 2m e e eh µ l = n = nµ B 2 m e Bohr magneton orbital angular Momentum quantized as integer times h µ B J T ( / ) Spin angular momentum of an electron e eh µ S S =± m 2m e e Orbital magnetic moment Spin magnetic moment 2 electron spin ±½h h 34 h = ( J s) 2π Planck s constant in external B field U = urur µ B Total Moment = µ l + µ s D-SCHOOL-05 12

13 STERN GERLACH EXPERIMENT- QUANTIZATION of SPIN J=S=1/2 D-SCHOOL-05 13

14 FROM ATOMS to SOLIDS D-SCHOOL-05 14

15 ATOMS in EXTERNAL FIELDS- QUANTIZATION D-SCHOOL-05 15

16 PAULI PRINCIPLE- 3d metals electronic configuration ΓΕΝΙΚΑ Ions Spin direction of 3d orbitals # electrons Mag. Moment Ti3+, V µ Β Principle quantum number n = 1, 2, 3,.. describes orbital size and energy Angular momentum quantum number l = 0 to n-1 describes orbital shape Magnetic quantum number m l = l, l-1 -l describes orientation in space of the orbital relative to the other orbitals in the atom Spin quantum number m s = +1/2 or -1/2 describes the direction of spin of the e - on its axis Pauli Exclusion Principle: "no two electrons in an atom can have the same set of quantum numbers", or, only two electrons (of opposite spin) per orbital. Ti2+, V µ Β V2+, Cr3+, Mn µ Β Cr2+, Mn µ Β Mn2+, Fe µ Β Fe2+, Co µ Β Co µ Β Ni µ Β Cu µ Β Zn2+, Cu µ Β D-SCHOOL-05 16

17 ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΚΑΙ ΥΨΗΛΗ ΤΕΧΝΟΛΟΓΙΑ: Από τη µαγνητική ροπή του ηλεκτρονίου σε εφαρµογές καθηµερινές και µελλοντικές D-SCHOOL-05 17

20 The magnetic periodic table YELLOW: GREEN: PINK: BLUE: GRAY: RED: ferromagnetic at room temperature widely encountered in magnetic compounds of some importance in magnetism of little importance in magnetism of little or no importance in magnetism magnetically inert D-SCHOOL-05 20

21 D-SCHOOL-05 21

22 ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΚΑΙ ΥΨΗΛΗ ΤΕΧΝΟΛΟΓΙΑ: Από τη µαγνητική ροπή του ηλεκτρονίου σε εφαρµογές καθηµερινές και µελλοντικές What determines the key properties of a magnetic material? (i) Magnetic moment per atom (ii) Magnetization* (iii) Curie temperature (iv) Magnetic anisotropy** D-SCHOOL-05 22

24 ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΚΑΙ ΥΨΗΛΗ ΤΕΧΝΟΛΟΓΙΑ: Από τη µαγνητική ροπή του ηλεκτρονίου σε εφαρµογές καθηµερινές και µελλοντικές (1) D-SCHOOL-05 24

28 ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΚΑΙ ΥΨΗΛΗ ΤΕΧΝΟΛΟΓΙΑ: Από τη µαγνητική ροπή του ηλεκτρονίου σε εφαρµογές καθηµερινές και µελλοντικές MAΓΝΗΤΙΚΕΣ ΠΕΡΙΟΧΕΣ Magnetic Domains in an Magnetic Domains in Garnet D-SCHOOL Amorphous Thin Film

29 Domain Wall Motion/Magnetization Rotation Ordinary Ferromagnetic Materials Consisting of Magnetic Domains D-SCHOOL-05 29

30 Hysteresis Loops Typical hysteresis loops [M(H) and B(H)] for a ferromagnetic material. (H c ) (M r ) (M s ) Area under loop represents the hysteresis losses. B=H+M D-SCHOOL-05 30

31 Soft and Hard Materials M H Soft Materials: Co, Ni, Fe, NiFe, etc. Low Anisotropy, low Hc Used where a high magnetic induction and low losses are required such as transformers. M Hard Materials: Sm-Co, NdFeB, CoPt, FePt, etc. H High anisotropy, High Hc Used where a high remanence is required such as permanent magnets D-SCHOOL-05 31

32 Permanent Magnets Hard magnets, also referred to as permanent magnets, are magnetic materials that retain their magnetism after being magnetized (retain alignment without the presence of external field). Energy has been stored in the magnets! The strongest hard magnets today are Nd-Fe-B and Sm-Co. The transition metals (Fe, Co) provide the high magnetization and the rare-earths (Nd, Sm) the high anisotropy. Maximum Energy product (BH) m is a parameter that characterizes the strength of a permanent magnet. (BH) m = (M r /2) 2 if H c =M r /2 D-SCHOOL-05 32

33 Development of (BH) max D-SCHOOL-05 33

34 Nanocomposite Magnets: Next Generation Magnets Consist of a fine mixture of soft and hard phases with enhanced remanence and energy products in the nanocomposites bulk Multilayers M M M Coarse mixture H H H Hard Phase High H c Soft Phase High M s Hard + Soft Fine mixture For optimum exchange coupling, D s =2 δ wh (10 nm for Nd-Fe-B) D-SCHOOL-05 34

35 ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΚΑΙ ΥΨΗΛΗ ΤΕΧΝΟΛΟΓΙΑ: Από τη µαγνητική ροπή του ηλεκτρονίου σε εφαρµογές καθηµερινές και µελλοντικές MAGNETIC RECORDING D-SCHOOL-05 35

36 Basic Principles of Magnetic Recording Longitudinal Recording D-SCHOOL-05 36

37 ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΚΑΙ ΥΨΗΛΗ ΤΕΧΝΟΛΟΓΙΑ: Από τη µαγνητική ροπή του ηλεκτρονίου σε εφαρµογές καθηµερινές και µελλοντικές MAGNETIC RECORDING RECORDING Writing data on a storage medium Reading data from a storage medium by GMR head D-SCHOOL-05 37

38 GMR- RECORDING HEADS D-SCHOOL-05 38

39 SPIN VALVE ANIMATION S1 AF P F S2 V sig =-JW ½ ρ cosθ θ = 180 θ =90 θ =90 θ =90 θ =0 D-SCHOOL-05 39

40 ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΚΑΙ ΥΨΗΛΗ ΤΕΧΝΟΛΟΓΙΑ: Από τη µαγνητική ροπή του ηλεκτρονίου σε εφαρµογές καθηµερινές και µελλοντικές Computational Micromagnetics MAGNETIC RECORDING Use uniform rectangular discretizations for both media and reader stack. Magnetization M is uniform in each cell. Magnetization damping follows Landau-Lifshitz-Gilbert Equation dm = γm H dt eff λ M s M ( M H γ = the gyromagnetic ratio of the free electron spin λ = damping constant eff ) H eff M D-SCHOOL-05 40

41 ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΚΑΙ ΥΨΗΛΗ ΤΕΧΝΟΛΟΓΙΑ: Από τη µαγνητική ροπή του ηλεκτρονίου σε εφαρµογές καθηµερινές και µελλοντικές MAGNETIC RECORDING D-SCHOOL-05 41

42 FUNDAMENTALS OF SPIN 1 In addition to their mass and electric charge, electrons have an intrinsic quantity of angular momentum called spin, almost as if they were tiny spinning balls. 2 Associated with the spin is a magnetic field like that of a tiny bar magnet lined up with the spin axis. 3 Scientists represent the spin with a vector. For a sphere spinning "west to east" the vector points "north" or "up." It points "down" for the opposite spin. 4 In a magnetic field, electrons with "spin up" and "spin down" have different energies. 5 In an ordinary electric circuit the spins are oriented at random and have no effect on current flow. 6 Spintronic devices create spin-polarized currents and use the spin to control current flow D-SCHOOL-05 42

43 SPINTRONICS D-SCHOOL-05 43

44 SPINTRONICS D-SCHOOL-05 44

45 ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΚΑΙ ΥΨΗΛΗ ΤΕΧΝΟΛΟΓΙΑ: Από τη µαγνητική ροπή του ηλεκτρονίου σε εφαρµογές καθηµερινές και µελλοντικές SPINTRONICS D-SCHOOL-05 45

46 MEMORIES and NEW MAGNETIC MEMORIES (MRAMS) D-SCHOOL-05 46

47 MEMORIES and NEW MAGNETIC MEMORIES (MRAMS) D-SCHOOL-05 47

48 ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΓΙΑ ΒΙΟ-ΙΑΤΡΙΚΕΣ ΕΦΑΡΜΟΓΕΣ D-SCHOOL-05 48

49 ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΚΑΙ ΥΨΗΛΗ ΤΕΧΝΟΛΟΓΙΑ: Από τη µαγνητική ροπή του ηλεκτρονίου σε εφαρµογές καθηµερινές και µελλοντικές Magnetic Separation-Biosampling GMR- Sensor D-SCHOOL-05 49

50 ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΚΑΙ ΥΨΗΛΗ ΤΕΧΝΟΛΟΓΙΑ: Από τη µαγνητική ροπή του ηλεκτρονίου σε εφαρµογές καθηµερινές και µελλοντικές Bio-Magnetic GMR Sensors Advantage over other sensing methods (Flurescent, Radioactive, etc.): Schematic of the GMR sensor elements, showing the binding of a magnetic nanoparticle to one or the sensor elements. Take advantage of GMR s sensitivity, low cost, and high density Constant signal Little background Insensitive to ambient light More compact than optical methods Can be manipulated externally D-SCHOOL-05 50

52 ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΚΑΙ ΥΨΗΛΗ ΤΕΧΝΟΛΟΓΙΑ: Από τη µαγνητική ροπή του ηλεκτρονίου σε εφαρµογές καθηµερινές και µελλοντικές BIOMEDICAL APPLICATIONS-HYPERTHERMIA FM particles possess hysteretic properties when exposed to a time varying magnetic field, which gives rise to magnetically induced heating. The amount of heat generated per unit volume is given by the frequency multiplied by the area of the hysteresis loop: D-SCHOOL-05 52

53 ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΚΑΙ ΥΨΗΛΗ ΤΕΧΝΟΛΟΓΙΑ: Από τη µαγνητική ροπή του ηλεκτρονίου σε εφαρµογές καθηµερινές και µελλοντικές Advantages of nanoparticles for MFH 60 High Specific Adsorption Rate compared to microparticles Cell MFH Size Targeting of Different Organs Temperature ( C) Time (seconds) Different Modification of Nanoparticles for the targeting of different cells Etc. D-SCHOOL-05 53

54 ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΚΑΙ ΥΨΗΛΗ ΤΕΧΝΟΛΟΓΙΑ: Από τη µαγνητική ροπή του ηλεκτρονίου σε εφαρµογές καθηµερινές και µελλοντικές MRI-Enchancement D-SCHOOL-05 54

55 ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΚΑΙ ΥΨΗΛΗ ΤΕΧΝΟΛΟΓΙΑ: Από τη µαγνητική ροπή του ηλεκτρονίου σε εφαρµογές καθηµερινές και µελλοντικές MRI With ΜαγνητικάNanoparticles Highly Sensitive in Detecting Prostate Cancer Metastases By Anthony J. Brown, MD NEW YORK Jun 18, 2003 (Reuters Health) - Highresolution MRI with magnetic nanoparticles is highly sensitive in detecting clinically occult lymphnode metastases in prostate cancer, according to a new report. In fact, routine use of this modality preoperatively could obviate many unneeded surgeries. MRI with nanoparticles correctly identified all of the patients with nodal disease. In addition, on nodeby-node analysis, the sensitivity of this modality, at 90.5%, was significantly higher than that of conventional MRI, at 35.4% (p < 0.001). D-SCHOOL-05 55

56 PM APPLICATIONS AT HIGH TEMPERATURES Selected current classes of materials.- MAGNETIC MATERIALS BULK MAGNETS-APPLICATIONS Ion Beam Thruster Fig. Xenon gas is delivered to the thruster, ionized, Accelerated and neutralized. D-SCHOOL-05 56

57 Deformable mirror for adaptive optics (astronomy, ophtalmology) Reflective layer z Flexible membrane Silicon ring ±5 µm r membrane magnets coils Magnets Array of planar micro-coils Silicon waffer Si 2" 19 coils Ø 6 mm (hexagonal array) (=> up to several 100 to 1000s pixels) D-SCHOOL-05 57

58 ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΚΑΙ ΥΨΗΛΗ ΤΕΧΝΟΛΟΓΙΑ: Από τη µαγνητική ροπή του ηλεκτρονίου σε εφαρµογές καθηµερινές και µελλοντικές A guide to Magnetism throughout the ages Τhe sevem moments of magnetism D-SCHOOL-05 58

59 ΜΑΓΝΗΤΙΚΑ ΥΛΙΚΑ ΚΑΙ ΥΨΗΛΗ ΤΕΧΝΟΛΟΓΙΑ: Από τη µαγνητική ροπή του ηλεκτρονίου σε εφαρµογές καθηµερινές και µελλοντικές ΕΥΧΑΡΙΣΤΙΕΣ Dr. D. Petridis Dr. A. Simopoulos Dr. P. Panagiotopoulos- U of Ioannina Dr. V. Karanasos Dr. C. Christides- U of Patras Dr. G. Hadjipanayis- U of Delaware Dr. L. Castaldi Dr. A. Tarvlos Dr. C. Giannakopoulos Dr. E. Devlin Dr. V. Tzitzios Dr. A. Speliotis Mr. E. Manios Mr. V. Alexandrakis D-SCHOOL Also Projects HIDEMAR DYNAMICS DYNASPIN M2EMS