OutlineWe will have a Monday class next weekSlide 3Slide 4Slide 5Behavior of magnetic materialsTypes of bulk magnetismDevelopment of permanent (hard) magnetsWhat is nanoscience?Slide 10Radius rulesArrangements of nanoparticles mimics arrangements of atomsSome arrangements are very complexElectronic and magnetic materials can be combined into sophisticated devicesMagnetiteSlide 16Slide 17Ferrofluids of ~10nm ferrite particlesFerrofluidsSlide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Ferrofluid topicsSlide 30Slide 31Outline•How is ferromagnetism manifested?•What are the types of magnetism? •What is Fe3O4 – spinel?•What is nanoscience?•How do we make ferrofluids?We will have a Monday class next week•Turn in extra credit•Writing exercises will be returned•Possible chance for regaining lost points•SRTI evaluationsS SSSNN NNThe field of a force – a property of the space in which the force actsMagnetic fieldattractionrepulsionhttp://www.trincoll.edu/~cgeiss/GEOS_312/GEOS_312.htmθInteraction with magnetic fieldm = AInm = pd+p-pdτ = m B sinθBθaligning torque: http://www.trincoll.edu/~cgeiss/GEOS_312/GEOS_312.htmMagnetic field (force lines)Magnetic field is not a central field (no free magnetic charges)SNFhttp://www.trincoll.edu/~cgeiss/GEOS_312/GEOS_312.htmBehavior of magnetic materialsTNeelTCurieFerromagnet, FerrimagnetAntiferromagnetParamagnetMagnetization(m or B or M)TemperatureTypes of bulk magnetismFerromagnetism AntiferromagnetismFerrimagnetismLarge M(1-5 B / atom)Small M(10-3 B / atom)Large M(1-5 B / atom)HSmall M(10-3 B / atom)ParamagnetismDevelopment of permanent (hard) magnetsMMhttp://www.tf.uni-kiel.de/matwis/amat/elmat_en/kap_4/backbone/r4_3_6.htmlHard magnets Soft magnetsWhat is nanoscience?Contacts on a 60nm bismuth wire to study motion of single defects (kmf.pa.msu.edu/Research/resrch04.asp )ZnO nanowire UV lasers of about 100nm diameter and 10mm length synthesized at Berkeley. (Yang et al, Science, 292, p. 1897, 2001).ZnO nanowire UV lasers of about 100 nm diameter and 10 m length synthesized at Berkeley.(Yang et al, Science, 292, p. 1897, 2001)Radius rulesCNRelative radiusVoid geometry Polyhedron name2 <15.5% Linear Line3 15.5% Triangular Triangle4 25.5% Tetrahedral Tetrahedron6 41.4% Octahedral Octahedron8 73.2% Cubic (BCC) Cube12 100% Cuboctahedral (HCP, CCP) Cuboctahedron•A sphere of this size (relative to the lattice of size of its neighbors) is just able to touch all off its neighbors for the void geometries below.•Similar considerations govern the formation of more complex structural arrangementsArrangements of nanoparticles mimics arrangements of atomsSome arrangements are very complexElectronic and magnetic materials can be combined into sophisticated devicesMagnetite•Magnetite vs. lodestone•General spinel formula: AB2O4A = 2+ metal, B = 3+ metal•1/2 of octahedral holes, 1/8 of tetrahedral holes filled on an approximate FCC oxygen lattice•Fe3O41 Fe2+ + 2 Fe3+•Inverse spinel B(AB)O4•Ferrimagnetic ordering at ~850KFe3O4•Synthesis: 2 FeCl3 + FeCl2 + 8 NH3 + 4H2O --> Fe3O4 + 8 NH4ClMagnetite (Fe3O4)Unit cell:A-sites (8 Fe3+)B-sites (8 Fe3+ and 8 Fe2+) FerrimagnetismNormal Spinel (ZnFe2O4) Inverse Spinel (Fe3O4)A BZn2+Fe3+Fe3+A BFe3+Fe3+Fe2+=>5µB5µB4µBDevelopment of permanent (hard) magnetsMagnetic energy (Gauss / m3)SteelMagnetic energy (Gauss / m3)SteelNd2Fe14BMMhttp://www.tf.uni-kiel.de/matwis/amat/elmat_en/kap_4/backbone/r4_3_6.htmlFerrofluids of ~10nm ferrite particlesFerrofluidsTypes of bulk magnetismFerromagnetism AntiferromagnetismFerrimagnetismLarge M(1-5 B / atom)Small M(10-3 B / atom)Large M(1-5 B / atom)HSmall M(10-3 B / atom)ParamagnetismFerromagnetism AntiferromagnetismFerrimagnetismHCanted AntiferromagnetismFerromagnetism AntiferromagnetismFerrimagnetismHCanted AntiferromagnetismFerromagnetism AntiferromagnetismHFerromagnetism AntiferromagnetismHFerrimagnetismFerrimagnetismParamagnetismParamagnetismFerromagnetism AntiferromagnetismFerrimagnetismLarge M(1-5 B / atom)Small M(10-3 B / atom)Large M(1-5 B / atom)HSmall M(10-3 B / atom)ParamagnetismTypes of magnetismFerrofluid topics•Magnetic dipoles, not monopoles like charges•Field gradient - emphasized by magnetic field lines•A “test dipole” will aligns itself parallel to magnetic field linesDevelopment of permanent (hard)