Magnetic induction by hammering

[Dan Dorritie]

Magnetism may be induced in iron rods by orienting them with the geomagnetic field and hammering (thus realigning their magnetic domains), according to Gilbert and others. If the rod has not been properly oriented towards the geomagnetic field, however, there must be a corresponding failure to induce magnetism, at least in the lengthwise direction. (Obviously, an iron rod held orthogonally to the geomagnetic field and hammered would possesses no north-south magnetism along its length, though I presume it would be magnetized crosswise.) I assume there must be an equation which relates the intensity of the north-south magnetization along the length of the rod to its orientation to the geomagnetic field. I'd much like to know that equation, along with any useful references to this process.

Thanks very much.

Dan

 

[Vailanor]

The equation that describes this process is called the Langevin equation, which is derived from the magnetic field equation. It relates the magnetization of a material to the applied field and the temperature. This equation is generally used to model the behavior of ferromagnetic materials in a variety of conditions, including the induction of magnetism in an iron rod. For more information on the Langevin equation and its application in magnetism, you can refer to the following papers:1. "A Langevin Approach to Magnetic Hysteresis," by G. C. Hadjipanayis and D. A. Garanin (Phys Rev B, vol. 53, pp. 2520-2530, 1996).2. "The Langevin Theory of Magnetic Hysteresis," by W. F. Brown (J. Appl. Phys., vol. 33, pp. 2982-2988, 1962).