1. Howard H. Liebermann, Ph.D.

2.  Structure of Metals  On atomic level, regular arrangement of atoms immersed in “sea” of “free electrons”.  Results of this:  Metallic bond  Electrical, thermal conductivity  Ductility  Typical arrangements of atoms:  BCC, FCC, HCP  Atypical arrangement of atoms:  Amorphous H.H. Liebermann2

3. 3 FCC BCCSimple Cube

4.  Electron has negative charge  Orbiting of electrons about atom induces magnetic moment (vector)  These magnet moments can interact  with one another  with an external applied magnetic field  Extent of interaction determines what kind of magnetism (exchange vs. anisotropy) H.H. Liebermann4

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7.  Ferromagnetism: magnetic spin interaction is large – applied external magnetic field doesn’t affect this  Paramagnetism: magnetic spins tend to align in the direction of applied field  Diamagnetism: magnetic spins tend to align in the direction away from applied field H.H. Liebermann7

8.  Exchange - strong interaction between magnetization vectors  Anisotropy – preferential direction for magnetization vector in a material  Magnetostriction – interaction between stress (applied, residual, etc.) and magnetization vector direction H.H. Liebermann8

9.  Temperature above which sample magnetization ceases.  True for ferromagnetic, paramagnetic, etc.  Potential in sensor applications. H.H. Liebermann9

10.  Quantum mechanical effect:  Tendency for adjacent magnetic vectors to align directionally.  Affected by thermal energy. H.H. Liebermann10

11.  Origin:  Tropy – direction  Iso – constant  An – not  Conclusion – not constant with direction in an alloy.  Magnetic anisotropy result of:  Crystal structure of alloy.  Shape of sample being tested.  Magnetic field induced. H.H. Liebermann11

12.  Link between change in magnetic sample dimensions (stress) and applied magnetic field.  Reciprocity abounds.  Stress can result from numerous causes:  Forces applied to magnetic sample.  Residual forces resulting from cooling on heat treating.  Forces arising during use of a device. H.H. Liebermann12

13.  Iron  Cobalt  Iron + Cobalt H.H. Liebermann13

14. w ~ H.H. Liebermann14 ε K

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16.  No external field (applied, residual, etc.) and magnetization vector direction  Low external field  High external field H.H. Liebermann16

17.  Rotational  Reverse domain nucleation  Eddy current generation  Magnetic losses  Electrical losses  Heat losses H.H. Liebermann17

18. HardSoft robust magnetic field easily demagnetized largely impervious to external fields high permeability can be costly switching applications provide strong field H.H. Liebermann18

19. HardSoft stators/rotors low loss transformers motors/generators inductors (various) EAS (bias alloy) Invar (Fe-Ni) alloys refridge door gaskets, etc. nanocrystalline toys Maglev train H.H. Liebermann19

20. Field of Application Products RequirementsMaterials Permanent Magnets Loudspeakers Small generators/motors Sensors Large H C and M R Fe-based Fe+ ~(0.7–5)% Si Fe +~(35-50)%Co Analog Data Storage Video tape Audio tape Medium H C and M R (hysteresis loop square) Fe/Co/Ni/Al/Cu = 50/24/14/9/3 SmCo 5 Sm 2 Co 17 Nd 2 Fe 14 B Digital Data Storage Hard, floppy disc Bubble memory Special magnetic domain structure NiCo, NiCoFe CrO 2 Fe 2 O 3 H.H. Liebermann20

21. Field of Application Products RequirementsMaterials Analog Data Storage Video tape Audio tape Medium H C and M R (square hysteresis loop) Fe/Co/Ni/Al/Cu = 50/24/14/9/3 SmCo 5 Sm 2 Co 17 Nd 2 Fe 14 B Digital Data Storage Hard, floppy disc Bubble memory Special magnetic domain structure Ni/Co, Ni/Co/Fe CrO 2 Fe 2 O 3 H.H. Liebermann21

22. Field of Application Products RequirementsMaterials Power Conversion Motors Generators Electromagnets Large M R Small H c Losses low Fe-based Fe+ ~(0.7–5)% Si Fe +~(35-50)%Co Power Adaptation Power Transformers H.H. Liebermann22

23. Field of Application Products RequirementsMaterials Signal Transfer Other Transformers Linear M-H curve LF (<100kHz) Low conductivity Fe+36%Fe/Ni/Co = 20/40/40 HF (>100kHz) Very low conductivity Ni–Zn ferrites Magnetic Shielding/EAS Permalloy Mu metal Large dM/dH @ H=0 Ni/Fe/Cu/Cr ~77/16/5/2 H.H. Liebermann23

24.  Wide variety of materials/applications.  Elementary concepts of materials science as they apply to magnetic materials.  Aspects of alloy design (chemistry) and resulting effects on magnetic properties. H.H. Liebermann24