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Thin magnetic films occupy a special place in the problem of pulsed remagnetization of ferromagnets. The straight-through domain structure, the slight effect of eddy currents, and a number of other peculiarities make films convenient objects for studying the nature of pulsed remagnetization. This article presents a review of the basic results of study of the pulse properties of uniaxial polycrystalline films. The basic theoretical papers relate to the case of remagnetization of films by coherent rotation of the magnetization. A discussion of the question of the relation of the coherent-rotation model to the behavior of the real films comes up against an absence of information about the nature of the energy losses in pulsed remagnetization, and also an absence of reliable experimental data on the conditions under which nearly coherent rotation actually takes place in films. Attention is paid to significant successes in the development of methods for observing the nonequilibrium dynamic domains that originate in the process of pulsed remagnetization. The realization of these methods and the creation of setups with display times 10-8–10-9 sec have made possible an appreciable advance in the study of the nature of incoherent rotation and of domain-wall displacement—the basic mechanisms of the remagnetization of films.

Palaeomagnetic properties of igneous rocks in relation to their thermal history are discussed. Owing to a longlasting and complicated thermal history of most igneous formations it is suggested that in general the original thermoremanence has been replaced by a viscous build-up at moderate temperatures. Following this suggestions it seems impossible to establish a magnetization/time relationship within most igneous units rendering several potential palaeomagnetic and geological applications of rock magnetism unlikely to apply. It appears that under certain circumstances remagnetization may upset the original direction in a very complicated manner. Finally, the remagnetization theory may provide a satisfactory explanation of the apparent petrology/polarity correlation.

Aspects and examples of chemical remagnetization are dealt with. This type of remagnetization is likely to be a significant one in rocks laid down in low palaeolatitudes but may also be of general importance in intrusives, accompanying for instance post-emplacement hydrothermal alterations. There may be no significant stability difference between primary and secondary components and consequently the net magnetizations, which may define strongly deviating directions, may easily be wrongly considered as palaeomagnetic directions. In particular, the late Palaeozoic palaeomagnetism for Europe is discussed in some detail suggesting that fundamental problems associated with the magnetization of the rocks considered have been overlooked.

Magnetization curves and hysteresis loops of anisotropic hard ferrites were analyzed after the specimens had been demagnetized either thermally or by an ac field parallel or perpendicular to the preferred axis (PA) between -196°C and Curie temperature, or by a dc field. Each demagnetization yields a specific magnetization curve; below saturation fields, asymmetrically positioned and noncentrosymmetrical loops develop, except after ac demagnetization at 20°C (=measuring temperature) parallel to PA. This is due to domain configurations differently arranged and of different stability. The asymmetry is caused by "frozen" unstable configurations, which undergo an irreversible change due to the action of the field. Therefore, with reversed field not all of the previous possibilities for remagnetization are still available.

The directions of natural remanent magnetization of Old Red Sandstone rocks from five sites in south Wales where the strata are steeply inclined to the horizontal are significantly different from the average direction of magnetization of Old Red Sandstone rocks from flat-lying sites. The hypothesis, that the observed directions of magnetization are resultants of a primary component acquired in the Devonian and a secondary component acquired after folding, either in the Permian or Triassic, is shown to be tenable. A statistical technique, whereby the significance of the normal to the best-fitting plane through the observed and the supposed primary and secondary mean directions, is described. Ovals of confidence surrounding these normals are also calculated. Partial remagnetization of these rocks is shown to be slightly more probable in the Triassic than in the Permian at four out of five sites considered.

The remagnetization time τ has been measured as a function of external field H for a series of manganese ferrites, Mn1+xFe2−xO4. The physical properties of these compounds which enter into the domain wall model of Menyuk and Goodenough and the rotational model of Gyorgy have also been measured. It is found that α, the loss constant, is critical to the correlation of data with theory, and that neither theory can be unequivocally proved until more insight into the remagnetization process loss mechanism is acquired.

It is assumed that the velocity of the domain wall is proportional to the difference between the magnetic field intensity at the wall and the coercive force. The local magnetic field, which is not equal to the external field, is calculated from the eddy‐current equations. The rate of change of the magnetic flux as a function of time is determined. The total switching time is expressed in terms of two phenomenological constants: the retardation constant α mentioned above, and a delay time τ, the duration of the formative phase during which the plane walls are formed.

Measurements of the NRM (natural remanent magnetization) of Lower Ordovician sediments collected from both flanks of the Arbuckle anticline (south-central Oklahoma) correspond to an upper Carboniferous–Permian magnetization direction. Directions of magnetization are well grouped and remain essentially unchanged through thermal demagnetizations up to 400°C. Correction for folding indicates that the magnetization is post-folding and that the Arbuckle orogeny was of sufficient intensity to heat and remagnetize the sediments involved. Upon thermal demagnetization to temperatures of 550°C, the directions of magnetization changed considerably to directions distinctly removed from the observed upper Carboniferous–Permian direction. Sample in-in tensities are very weak and therefore a reliable direction was unattainable. The data form a streaked distribution away from the Carboniferous-Permian direction. The calculated upper Carboniferous–Permian pole, corrected for the primary prefolding remanence direction observed above 400°C, is located at 128.9° E., 46.1° N. Orogenic temperature calculations based on differing stabilities of this late Paleozoic remanence on opposite flanks of the anticline indicate a more intense orogeny to the north with minimum temperatures of 200°C. Lesser temperatures, of at least 120°C but less than 200°C, prevailed on the south flank.