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As the temperature increases up to the Curie temperature, the relative susceptibility of ferromagnetic materials?
Increases
Decreases
Remains constant
Becomes zero
Increases
As temperature increases up to the Curie temperature (TcтАЛ), thermal agitation reduces domain alignment, causing the magnetic permeability and relative magnetic susceptibility (urтАЛ) of ferromagnetic materials to gradually increase initially or follow the Curie-Weiss behavior near transition, before rapidly falling to paramagnetic levels above TcтАЛ. According to the Curie-Weiss Law, susceptibility is given by urтАЛтИТ1=TтИТTcтАЛCтАЛ for temperatures above TcтАЛ.
As temperature increases up to the Curie temperature (TcтАЛ), thermal agitation reduces domain alignment, causing the magnetic permeability and relative magnetic susceptibility () u_r)offerromagneticmaterialstograduallyincreaseinitiallyorfollowtheCurieтИТWeissbehaviorneartransition,beforerapidlyfallingtoparamagneticlevelsaboveT_c.AccordingtotheCurieтИТWeissLaw,susceptibilityisgivenby
urтАЛ - 1 = \frac{C}{T - T_c}$$ for temperatures above T_c$.
╧ЗmтАЛ=TтИТTcтАЛCтАЛ тАФ Curie-Weiss Law (for T>TcтАЛ)
╬╝rтАЛ=1+╧ЗmтАЛ тАФ Relation between relative permeability and magnetic susceptibility
In ferromagnetic materials, spontaneously aligned magnetic domains are held by exchange coupling. As thermal energy increases, domain walls move more easily initially under an applied field, leading to an effective increase in susceptibility before approaching the Curie point where thermal agitation completely destroys long-range ferromagnetic ordering.
Below Curie temperature (TcтАЛ), thermal agitation assists domain alignment under external field causing magnetic susceptibility to increase.
At Curie temperature (TcтАЛ), the ferromagnetic material undergoes a phase transition to become paramagnetic.
Above TcтАЛ, susceptibility decreases inversely with temperature following the Curie-Weiss law.
Option B is incorrect for temperature increases up to TcтАЛ, though susceptibility decreases sharply once TcтАЛ is exceeded.
Option C is incorrect because magnetic properties are strongly temperature-dependent.
Option D is incorrect as susceptibility becomes small and positive (paramagnetic) above TcтАЛ, not zero.
A is correct тАФ As temperature increases up to the Curie temperature, domain mobility increases under an applied magnetic field, causing relative susceptibility to increase.
In competitive exams, pay close attention to the specified range: 'up to Curie temperature' means susceptibility increases, while 'above Curie temperature' follows Curie-Weiss law where susceptibility decreases.