Register to reply

Paramagnetism of Free Ions. Sign problem.

by LagrangeEuler
Tags: free, ions, paramagnetism, sign
Share this thread:
Sep1-13, 11:10 AM
P: 316
Energy of system of magnetic dipoles is
##E_H=-\mu_0 \vec{\mu}\cdot \vec{H}=-\mu_0\mu_zH##
why sign ''-''?
and ##\mu_z=-g_J\mu_Bm##
Again why ''-'' sign ?
##z## is choosen to be quantization direction, and along that direction is applied field ##H##.
Phys.Org News Partner Physics news on
Interfaces within materials can be patterned as a means of controlling the properties of composites
A new, tunable device for spintronics
Researchers study gallium to design adjustable electronic components
Sep2-13, 11:22 AM
P: 34
E=m[itex]\bullet[/itex]B but as the material has a magnetization M and B= H+M then H must face the opposite direction to B and that explains the first negative sign I think.
M Quack
Sep17-13, 03:27 PM
P: 669
In a paramagnet, the magnetization of the material is parallel to the applied field. In a diamagnet it would be antiparallel (opposite).

The first "-" is there because the energy decreases when a magnetic moment is parallel to the applied field.

The second "-" does not make any sense to me.

H appears to be along the positive z direction. Then the magnetization mu_z should also be along the positive z direction, and it should be proportional to H. The magnitude of the magnetization also depends on the temperature.

Register to reply

Related Discussions
Will gaseous ionic compounds be free moving ions? Chemistry 3
Pauli Paramagnetism vs Curie Paramagnetism Atomic, Solid State, Comp. Physics 1
Isoelectronic Ions problem Biology, Chemistry & Other Homework 2
Need help with the sign of g in free fall acceleration Introductory Physics Homework 1
Free way Sign Problem - Statics Introductory Physics Homework 5