What is the result of increasing and then decreasing the H field strength around a material?

The process of increasing and then decreasing the H field strength, or magnetic field strength, around a material can lead to the phenomenon known as permanent magnetism. This occurs when the magnetic domains within a ferromagnetic material become aligned in the direction of the applied magnetic field during the increase in H field strength. Once the field is decreased, some of these domains may remain aligned, resulting in a material that retains a net magnetic moment, hence achieving permanent magnetism.

This behavior is particularly relevant in materials with high coercivity, which can maintain their magnetization even after the external magnetic field is removed. The history of the magnetic field applied to the material plays a critical role in determining the extent to which permanent magnetism is acquired.

The other options primarily deal with different physical phenomena or characteristics that do not directly relate to the behavior of magnetic fields and materials in the context of changing H field strength. Magnetostriction, for instance, involves the dimension change of a material in response to a magnetic field but does not inherently result from the magnetic field's strength variations in the same way. Decreasing dielectric strength and inducing current relate to electrical properties and responses, which are not the primary focus when discussing the effects of varying magnetic fields on materials.