Final answer:
The desirability of permanent magnetization depends on the application, with permanent magnets made up of aligned electron spins providing consistent magnetic fields, and electromagnets that offer magnetic fields on-demand via electric current. Permanent magnets can also lose magnetization through hard blows or heating above their Curie temperature.
Step-by-step explanation:
Whether it is desirable to have a permanent magnetization depends on the application. Permanent magnets are made by aligning the spinning electrons within a material, a process that André-Marie Ampère theorized as microscopic current loops before the discovery of the electron. This alignment is what gives permanent magnets their long-lasting magnetic properties. Ferromagnetic materials, when in the presence of a magnetic field, have their domains aligned, and this alignment can become locked, resulting in permanent magnetization, a phenomenon known as hysteresis. This can be beneficial for applications where a constant magnetic field is required without the need for an external power source. Conversely, there are situations where permanent magnetization is not desired, such as in applications which require control over the magnetic field presence, for instances through the use of an electromagnet, which utilizes electric current to produce a magnetic field only when needed.
Moreover, the ability to retain magnetization can be compromised, as hitting a permanent magnet with a hard blow or heating it above the Curie temperature can demagnetize it. The Curie temperature represents the threshold above which the thermal agitation surpasses the magnetic order, causing a loss of the ferromagnetic properties, and it varies for different materials. For example, the Curie temperature for iron, a common ferromagnetic material, is 1043 K (770°C).