Howard H. Liebermann, Ph.D.

 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 FCC BCCSimple Cube

 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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 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

 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

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

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

 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

 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

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

w ~ H.H. Liebermann14 ε K

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

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

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

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

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

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

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

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 H=0 Ni/Fe/Cu/Cr ~77/16/5/2 H.H. Liebermann23

 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