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SOFT & HARD MAGNETIC MATERIALS AND STONER-WOHLFARTH THEORY (HAZIQAH…
SOFT & HARD MAGNETIC MATERIALS
AND
STONER-WOHLFARTH THEORY (HAZIQAH 4 SSCZ)
Introduction
Ferromagnetic material
soft magnetic material
hard magnetic material
:check: typical magnetic
hysteresis loop
area under the hysteresis loops
:check: help to quantify them as hard
or soft magnetic materials
Hard magnetic materials
:<3: low initial permeability
:<3: used for disk media or for a permanent
magnet application
:<3: high coercive
force
soft magnetic materials
:star: low coercivity
:star: exhibit high initial permeability
:star: used for a transformer or a magnetic head
application
Stoner - Wohlfarth Theory
simple analytical model describing the hysteresis
Energy density
E total = Ku
sin2(phai)−uoMH cos (a−phai)
Minimize the Etotal with respect to thetha
:check: one or two energy minima
:check: array of non-interacting magnetic
particles with a random distribution
possible relation
:check: between two remanence curves
for the system of non-interacting particles
:check: Mr obtained by applied field into virgin state
:check: reduce it to zero
Soft magnetic material
:explode: easy to magnetize and demagnetize
:explode: low retentivity
:explode: Low coercivity
:explode: High permeability
:explode: High magnetic saturation
:explode: used for transformer and inductances core
:explode: Desirable for electromagnets
Hard magnetic material
:pencil2: called permanent magnet material
:pencil2: high retentivity
:pencil2: High Coercivity
:pencil2: High permeability
:pencil2: High magnetic saturation
:pencil2: High Curie point or temperature
:pencil2: High hysteresis losses
