Chapter 8: Q. 8.19 (page 345)
The critical temperature of iron is . Use this value to make a rough estimate of the dipole-dipole interaction energy , in electron-volts.
Short Answer
The dipole interaction energy of iron =
/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none}
Learning Materials
Features
Discover
Chapter 8: Q. 8.19 (page 345)
The critical temperature of iron is . Use this value to make a rough estimate of the dipole-dipole interaction energy , in electron-volts.
The dipole interaction energy of iron =
All the tools & learning materials you need for study success - in one app.
Get started for free
At T = 0, equation 8.50 says that . Work out the first temperature-dependent correction to this value, in the limit . Compare to the low-temperature behaviour of a real ferromagnet, treated in Problem 7.64.
Starting from the partition function, calculate the average energy of the one-dimensional Ising model, to verify equation 8.44. Sketch the average energy as a function of temperature.
For a two-dimensional Ising model on a square lattice, each dipole (except on the edges) has four "neighbors"-above, below, left, and right. (Diagonal neighbors are normally not included.) What is the total energy (in terms of ) for the particular state of the square lattice shown in Figure 8.4?

Figure 8.4. One particular state of an Ising model on a square lattice (Problem 8.15).
Consider an Ising model in the presence of an external magnetic field B, which gives each dipole an additional energy of B if it points up and B if it points down (where is the dipole's magnetic moment). Analyse this system using the mean field approximation to find the analogue of equation 8.50. Study the solutions of the equation graphically, and discuss the magnetisation of this system as a function of both the external field strength and the temperature. Sketch the region in the T-B plane for which the equation has three solutions.
Use a computer to plot as a function of kT/, as predicted by mean field theory, for a two-dimensional Ising model (with a square lattice).
What do you think about this solution?
We value your feedback to improve our textbook solutions.