Rock magnetism is the study of the behaviour and magnetic properties of different types of rocks and their constituent minerals, as found in nature. The magnetic characterisation of a sample requires the measurement of several parameters, some of the most important being:

- Magnetic susceptibility.

- Magnetic hysteresis cycles. From them, different parameters can be calculated, such as the saturation magnetisation (Ms), the coercivity (Hc), the saturation remanent magnetisation (Mrs), etc. Also, the shape of the cycles themselves provides information about the nature and possible coexistence of various ferromagnetic minerals.

- IRM (Isothermal Remanent Magnetization) acquisition and demagnetisation curves. From these, parameters such as remanence coercivity (Hcr), saturation remanent magnetisation (Mrs), S-ratio, etc. are calculated, which give information on the nature of the ferromagnetic minerals present in the rock.


- Thermal demagnetisation of an IRM imparted on three orthogonal axes. It allows simultaneous characterisation of the coercivities and unlocking temperatures of the magnetic phases present in the rock.

- ARM (Anyisteretic Remanent Magnetization) acquisition and demagnetization curves.

- Thermomagnetic or Curie curves. These allow characterisation of the Curie and/or chemical transformation temperatures of the ferromagnetic minerals in the rock.



- Low temperature measurements. They allow the characterisation of various low-temperature phase transitions (Verwey, Morin, etc.), and also the relative importance of the superparamagnetic fraction.


All these parameters provide fundamental information to identify the different ferromagnetic minerals present in a sample and their magnetic state (superparamagnetic, monodomain, pseudo-monodomain, multidomain), which depends mainly on the size and shape of the grains or crystals.

Rock magnetism studies, whether complete or partial, are usually carried out in addition to any palaeomagnetic study, in order to find out which are the ferromagnetic minerals carrying the NRM, as this may have important implications on the origin, stability and history of that NRM.

Furthermore, rock magnetism is an interesting field of research per se, to understand the microphysics of minerals. It is also a fundamental tool for environmental or palaeoenvironmental magnetism studies, which attempt to characterise the magnetic phases present in recent or ancient sediments and their variation, both spatially and temporally. Given the connection between environmental or palaeoenvironmental parameters and the presence and state of one or another ferromagnetic mineral, this allows us to extract important environmental or palaeoenvironmental information. Examples of this type of applications of rock magnetism (see corresponding sections in "Lines of Research") include work on urban air pollution from particles deposited on tree leaves, or the study of sediments from the Cretaceous-Tertiary boundary.

Some of the most recent works developed in this field by the Paleomagnetism Group are:


J. López-Sánchez, A. Palencia-Ortas, A. del Campo, G. McIntosh, M. Kovacheva, F. Martín-Hernández, N. Carmona, O. Rodríguez de la Fuente, P. Marín, A. Molina-Cardín and M. L. Osete (2020). Further progress in the study of epsilon iron oxide in archaeological baked clays. Physics of the Earth and Planetary Interiors, 307(July), 106554. DOI: 10.1016/j.pepi.2020.106554

F. Martín-Hernández, E.C. Ferré, S.A. Friedman (2014) Remanent magnetization in fresh xenoliths derived from combined demagnetization experiments. Tectonophysics, 624-625, 24-31. DOI: 10.1016/j.tecto.2014.04.006

F. Martín-Hernández, S. Guerrero-Suárez (2012) Magnetic anisotropy of hematite single crystals: high field experiments. International Journal of Earth Sciences, 101, 637-647. DOI: 10.1007/s00531-01130665-z