Comparison of B-versus-H behaviors for ferromagnetic/ferrimagnetic and diamagnetic/ paramagnetic materials
Comparison of B-versus-H behaviors for ferromagnetic/ferrimagnetic and diamagnetic/ paramagnetic materials
THE INFLUENCE OF TEMPERATURE ON MAGNETIC BEHAVIOR
• The saturation magnetization is a maximum at 0 K
• Curie temperature, Tc, the saturation magnetization diminishes
gradually and then abruptly drops to zero
• temperatures above Tc both ferromagnetic and ferrimagnetic
materials are paramagnetic
• for iron, cobalt, nickel, and Fe3O4, the respective values are 768,
1120, 335, and 585oC
• Antiferromagnetism is also affected by temperature; this
behavior vanishes at what is called the Néel temperature.
• At temperatures above this point, antiferromagnetic
materials also become paramagnetic
DOMAINS
Magnetisation Curve
Essential Characteristics of a Permanent Magnetic Material After it has been Magnetised
1 Coercive Force
2 Residual Magnetism or Remanence
3 Energy Product Value
1 Coercive Force : It is a measure of materials
resistance to demagnetisation by electrical means
2 Residual Magnetism or Remanence : It relates to the
intensity of magnetism remaining in the magnet after
the magnetic field has been switched off
3 Energy Product Value: It is virtually the quantity of
energy stored in the magnet following magnetisation
It is derived from the demagnetisation curve RC
HYSTERESIS
This lagging of the flux
density B with respect to
the magnetising field H is
called Hysteresis
OR represents remanent
magnetism or remanence, Br
SOFT & HARD MAGNETIC MATERIALS
HARD MAGNETIC MATERIALS
PROPERTIES OF SOFT AND HARD MAGNETIC MATERIALSSOFT MAGNETIC MATERIALS
Have High Permeability
Magnetic Energy Stored is not High
Have Negligible Coercive Force
Have low Remanance
Have low Resistivity and low Hysteresis loss
HARD MAGNETIC MATERIALS
Possess High Value of Energy Product i.e. BH value
Have High Retentivity and High Coercivity
Have strong Magnetic Reluctance
Have Hysteresis Loop Rectangular in Shape
Have Low Initial Permeability and High Hysteresis Energy Loss