The exchange coupling as being responsible for ferromagnetism is not the mutual magnetic interaction between two elementary magnetic dipoles. To show this, calculate (a) the magnitude of the magnetic field a distance of 13 nm away, along a dipole axis, from an atom with magnetic dipole moment 1.2 xx 10^(-23) \ J/T, and (b) the minimum energy required to turn a second identical dipole end for end in this field.

bruinhemd3ji

bruinhemd3ji

Answered question

2022-11-06

The exchange coupling as being responsible for ferromagnetism is not the mutual magnetic interaction between two elementary magnetic dipoles. To show this, calculate (a) the magnitude of the magnetic field a distance of 13 nm away, along a dipole axis, from an atom with magnetic dipole moment 1.2 × 10 23   J / T, and (b) the minimum energy required to turn a second identical dipole end for end in this field.
a) Number ()Units
b) Number ()Units

Answer & Explanation

avuglantsaew

avuglantsaew

Beginner2022-11-07Added 15 answers

dipole moment m = 1.2 × 10 23   J / T
The distance d = 13 n m = 13 × 10 9   m
The magnetic field along the axis is
B = μ 0 4 π 2 m d 3 = 4 π × 10 7 × 1.2 10 23 2 π × ( 13 × 10 9 ) 3 = 1.092 × 10 6   T
b)The energy in magnetic field B to retale a dipole m to angle 0 is
U = m B cos θ
Here to rotate θ = 180
minimum energy
U = m B cos 180 = 1.2 × 10 23 × 1.092 × 10 6 × ( 1 ) = 1.31 × 10 29   J

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