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Ferrimagnetic minerals have properties that modify the frequency spectrum in rocks. Ferrimagnetic minerals are divided into three main types: single-domain or superparamagnetic, multi-domain and pseudo-single domain. They are abundant in sedimentary rocks such as shales, sandstones and other mud-type deposits.
Single-domain ferrimagnetic minerals, also known as superparamagnetic minerals, are minerals with a single high-energy domain boundary. These high-energy boundary domains are magnetically aligned with each other, resulting in a low overall coercivity. Single-domain ferrimagnetic minerals can also occur as deformed grains, in which the high-energy domains are randomly distributed throughout the grains. When these grains are exposed to a magnetic field, they can become magnetized, although the field strength must be greater than the coercivity of the individual domains.
Multi-domain ferrimagnetic minerals contain multiple domain boundaries, which allow the minerals to become strongly magnetized in the presence of a magnetic field. Multi-domain ferrimagnetic minerals are abundant in sedimentary rocks, and they often form large grain sizes that can be detected easily in the field. Multi-domain ferrimagnetic minerals also have high coercivities and can be used for paleomagnetic studies.
Pseudo-single domain (PSD) ferrimagnetic minerals are similar to single-domain ferrimagnetic minerals, but instead of high-energy domain boundaries,PSD ferrimagnetic minerals have low-energy domain boundaries. As a result, they can be magnetized more easily and can remain magnetized even in the absence of a magnetic field. The coercivity of PSD ferrimagnetic minerals is generally much lower than that of either single-domain or multi-domain ferrimagnetic minerals, making them attractive for paleomagnetic studies.
Ferrimagnetic minerals are important for both paleomagnetic studies and environmental sensing. Because of their ability to modify the frequency spectrum in rocks, they provide useful information about the composition of rocks and the presence of various magnetic fields. They also have application in geophysical exploration, since their magnetization can be used to detect changes in subsurface structures. In addition, ferrimagnetic minerals can be used to detect and monitor environmental contamination, such as underground oil and gas deposits. Finally, because of their high coercivity, ferrimagnetic minerals are often used in permanent magnets.
