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