THE MAGNETOSTRICTION OF INVAR-ALLOYS

The principles of the theory of a phase transition into a magnetically ordered state are formulated for Invar alloys and other similar inhom ogeneous ferromagnets, for which the concept of a local Curie temperat ure distribution corresponding to the experimentally observed broadene d temperature interval of the transition into the ferromagnetic state has existed for 10 years. A method is proposed for obtaining informati on about the local temperature distribution from experimental data on the change in the properties of magnets in response to a change in tem perature. For iron-nickel-chromium alloys it is shown how to obtain th e temperature dependence of the magnetostrictional susceptibility of t he paraprocess from data on the magnetic contribution to the thermal e xpansion coefficient. This confirms the important role of the local Cu rie temperature distribution, and it also indicates a need for new ana lysis of experimental data on temperature-broadened magnetic ordering phase transitions. (C) 1998 American Institute of Physics.