^{Addendum I}

The cause of magnetic hysteresis (MH) has not been found by the current theory. Sixteen authors (cond-mat/0611542) start their article by asking "What causes MH?" and properly state that MH is fundamental to magnetic storage technologies and a cornerstone to the present information age. They found that all the "beautiful theories of MH based on random microscopic disorder" failed to explain their data. So, they produced new theories. Their answer to the above question was: "New advances in our fundamental understanding of MH are needed". Neither that article, nor other extensive work on the topic, such as 2160 pages of the 3-volume book "The Science of Hysteresis" (Academic Press, 2006) were able to find the cause of the phenomenon. Further attempts based on the current theory are futile.

The search, however, continues – without reference to the detailed explanation of the cause of MH, as well as the accounting for its major manifestations, put forward in 2001 in this book. All this became possible in terms of the new fundamentals of ferromagnetism emerged as a result of investigation of solid-state phase transitions. The latter were found to be nucleation in crystal defects and growth by rearrangement at interfaces in all instances. The concept of the new fundamentals of ferromagnetism is simple. When crystal structure changes, so do its physical properties, magnetization included. Change in magnetization resulted from the change of crystal structure, and not the other way round. Orientation of spins in a crystal lattice is set by the orientation of particles carrying them. In case of structural rearrangements at domain interfaces (e. g., under the action of external magnetic field), the new state of magnetization resulted from the new orientation of crystal lattice and its constituent particles. This new concept instantly eliminated major problems ferromagnetism faced:

¨  STABILITY OF FERROMAGNETIC STATE. In order to explain why a system of parallel spins is stable the (very strong) Weiss/Heisenberg’s molecular / exchange field was introduced. But it has failed on many levels, including wrong sign of the exchange integral. SOLUTION: The molecular field does not exist. Contribution of magnetic interaction to the total crystal free energy is small as compared to that of chemical bonding and other components. A ferromagnetic crystal is stable due to lover total energy in spite of a small destabilizing effect of the magnetic interaction.

¨  DISPARITY WITH FERROELECTRICITY. Ferromagnetism and ferroelectricity are very similar phenomena with analogous set of manifestations. The standard theory was unable to find a unified approach to them since Weiss/Heisenberg molecular field was applied only to ferromagnetism. No analog to it was found (or even needed) for ferroelectricity. SOLUTION: This profound inconsistence disappeared after the Weiss/Heisenberg molecular field was eliminated from consideration. Now the two phenomena can have parallel explanations.

¨  FIRST-ORDER FERROMAGNETIC PHASE TRANSITIONS. The current theory treats ferromagnetic phase transitions as second-order (critical phenomenon), but sufficiently accurate experimental studies find them to be first order (consequently, not a critical phenomenon). The attempts to incorporate first-order phase transitions by the theory defy logic. SOLUTION: All phase transitions in solid state, ferromagnetic or not, are nucleation and crystal growth. As to the few remaining "second-order" phase transitions, they are destined to be re-classified.  

¨  ORIGIN OF MH. Interpretation of magnetization as rotation of spins in the crystal structure makes reasonable explanation of MH impossible. SOLUTION: MH is that of structural rearrangements at interfaces, both in ferromagnetic phase transitions and magnetization of domain systems. The structural phase transitions require 3-D nucleation to start; both processes require 2-D nucleation to proceed. The nucleation is heterogeneous, localized in specific crystal defects – microcavities – where nucleation lags are encoded. These nucleation lags are the cause of MH.

The explanation of the cause of magnetic hysteresis is a constituent part of the new fundamentals of ferromagnetism consistently accounting also for the related phenomena: HYSTERESIS LOOPS, MAGNETIZATION, DOMAIN STRUCTURE, BARKHAUSEN EFFECT, MEMORY, "BLOCH WALL", MAGNETOSTRICTION, CURIE TEMPERATURE WITH MYSTERIOUS Cp-λ-PEAK, more… All that also remains "unnoticed": search for the cause of MH continues.